Docs: fill documentation gaps found in user questions

Add pages on class-hierarchy/smart-pointer/variant/chrono recipes, working without exceptions, and large, streamed and partial input. Extend the FAQ (23 entries, Known bugs first), parse error documentation (empty-input checklist, line/column, diagnostic positions), element access, conversions, creating values, ADL troubleshooting, memory, and build/distribution notes. Add 14 examples with generated output. Correct the statement that parse errors cannot be recovered from with -fno-exceptions. The topics come from recurring questions on Stack Overflow, Reddit, Hacker News, YouTube, and the project's GitHub discussions and issues. Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Silence an Infer false positive in json_view materialize (#5905 )
2026-10-24 23:08:56 +00:00 · 2026-10-24 19:13:49 +02:00 · 2026-10-24 17:10:31 +02:00 · 2026-10-24 07:41:21 +02:00 · 2026-10-24 07:41:06 +02:00 · 2026-10-24 07:38:17 +02:00
133 changed files with 22560 additions and 597224 deletions
@@ -18,7 +18,8 @@ environment:
  matrix:
    # The Visual Studio 2017 jobs compile everything with /std:c++17, so they
    # only build the C++17 variant of each test, split into two jobs each to
-    # stay below AppVeyor's 60-minute limit per job.
+    # stay below AppVeyor's 60-minute limit per job. The Visual Studio 2019
+    # job builds the tests for all standards and is split for the same reason.
    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
      configuration: Debug
      platform: x86
@@ -50,7 +51,13 @@ environment:
      configuration: Release
      platform: x86
      CXX_FLAGS: "/W4 /WX"
-      CMAKE_OPTIONS: "-DJSON_ImplicitConversions=OFF"
+      CMAKE_OPTIONS: "-DJSON_ImplicitConversions=OFF -DJSON_TestShard=0/2"
+      GENERATOR: Visual Studio 16 2019
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
+      configuration: Release
+      platform: x86
+      CXX_FLAGS: "/W4 /WX"
+      CMAKE_OPTIONS: "-DJSON_ImplicitConversions=OFF -DJSON_TestShard=1/2"
      GENERATOR: Visual Studio 16 2019

    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
@@ -64,6 +64,7 @@ labels:
    - "tests/src/unit-json_view.*"
    - "tests/src/json_view_test_helpers\\.hpp"
    - "tests/src/fuzzer-(parse_json_view|json_view_image)\\.cpp"
+    - "tests/benchmarks/json_view/.*"
    - "tools/amalgamate/config_json_view\\.json"
    - "docs/mkdocs/docs/features/json_view\\.md"
    - "docs/mkdocs/docs/api/basic_json_(document|view)/.*"
@@ -154,6 +154,28 @@ jobs:
          # PR content in a job without credentials.
          python3 tools/generate_natvis/generate_natvis.py $MAIN_DIR

+      - name: Check the nlohmann_json.natvis generator options
+        run: |
+          cd $MAIN_DIR
+          # The options for configurations outside the checked-in file write
+          # to a temporary file, so they do not affect the diff below.
+          GENERATOR=tools/generate_natvis/generate_natvis.py
+          python3 $GENERATOR --list-tags
+          TAG_COUNT=$(python3 $GENERATOR --list-tags | wc -l)
+
+          python3 $GENERATOR --abi-tags diag,_dp,_vns --abi-tags _diag --output $RUNNER_TEMP/abi_tags.natvis
+          grep -q '<!-- Namespace nlohmann::json_abi_diag_dp_vns -->' $RUNNER_TEMP/abi_tags.natvis
+          grep -q '<!-- Namespace nlohmann::json_abi_diag_dp_vns_v[0-9_]* -->' $RUNNER_TEMP/abi_tags.natvis
+          test $(grep -c '<!-- Namespace ' $RUNNER_TEMP/abi_tags.natvis) -eq $(( $(grep -c '<!-- Namespace ' nlohmann_json.natvis) + 2 ))
+
+          python3 $GENERATOR --all --output $RUNNER_TEMP/all.natvis
+          test $(grep -c '<!-- Namespace ' $RUNNER_TEMP/all.natvis) -eq $(( (1 << TAG_COUNT) * 2 + 1 ))
+
+          if python3 $GENERATOR --abi-tags _unknown --output $RUNNER_TEMP/unknown.natvis; then
+            echo "generate_natvis.py accepted an unknown ABI tag"
+            exit 1
+          fi
+
      - name: Build patch and check for differences
        id: diff
        run: |
@@ -38,14 +38,14 @@ jobs:

    # Initializes the CodeQL tools for scanning.
    - name: Initialize CodeQL
-      uses: github/codeql-action/init@24c54180a607b1449ed407dd24f251e4e9147c8d # v4.38.3
+      uses: github/codeql-action/init@6f2ac81f5cd81fe351a197ba0b00d91d03cd2aee # v4.39.0
      with:
        languages: c-cpp

    # Autobuild attempts to build any compiled languages  (C/C++, C#, or Java).
    # If this step fails, then you should remove it and run the build manually (see below)
    - name: Autobuild
-      uses: github/codeql-action/autobuild@24c54180a607b1449ed407dd24f251e4e9147c8d # v4.38.3
+      uses: github/codeql-action/autobuild@6f2ac81f5cd81fe351a197ba0b00d91d03cd2aee # v4.39.0

    - name: Perform CodeQL Analysis
-      uses: github/codeql-action/analyze@24c54180a607b1449ed407dd24f251e4e9147c8d # v4.38.3
+      uses: github/codeql-action/analyze@6f2ac81f5cd81fe351a197ba0b00d91d03cd2aee # v4.39.0
@@ -37,6 +37,14 @@ jobs:
            var matchArtifact = artifacts.data.artifacts.filter((artifact) => {
              return artifact.name == "pr"
            })[0];
+            // a run that failed before its jobs started (e.g. a stale queued
+            // run cancelled long after its push) has no artifact to report on
+            if (!matchArtifact) {
+              core.notice('Run ${{ github.event.workflow_run.id }} has no "pr" artifact; nothing to comment on.');
+              core.setOutput('found', 'false');
+              return;
+            }
+            core.setOutput('found', 'true');
            var download = await github.rest.actions.downloadArtifact({
               owner: context.repo.owner,
               repo: context.repo.repo,
@@ -51,9 +59,11 @@ jobs:
      # Extract the untrusted PR artifact into a dedicated empty directory and
      # read only the two expected files by fixed path afterwards. This avoids a
      # malicious archive overwriting workspace files or escaping via ../ paths.
-      - run: unzip -o pr.zip -d ./pr_artifact
+      - if: steps.download.outputs.found == 'true'
+        run: unzip -o pr.zip -d ./pr_artifact

      - name: 'Comment on PR'
+        if: steps.download.outputs.found == 'true'
        uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
        with:
          github-token: ${{ secrets.GITHUB_TOKEN }}
@@ -47,6 +47,6 @@ jobs:
          output: 'flawfinder_results.sarif'

      - name: Upload analysis results to GitHub Security tab
-        uses: github/codeql-action/upload-sarif@24c54180a607b1449ed407dd24f251e4e9147c8d # v4.38.3
+        uses: github/codeql-action/upload-sarif@6f2ac81f5cd81fe351a197ba0b00d91d03cd2aee # v4.39.0
        with:
          sarif_file: ${{github.workspace}}/flawfinder_results.sarif
@@ -0,0 +1,84 @@
+name: "json_view benchmarks"
+
+# On demand only: runs the comparison of json_view with yyjson, simdjson, and
+# Boost.JSON (tests/benchmarks/json_view/compare.py) on GitHub-hosted runners,
+# for numbers from x86-64 and AArch64 Linux. It runs when started by hand, or
+# when a pull request gets the label "benchmark" (on both architectures, with
+# GCC and the default settings). Shared runners are noisy: the results show
+# where json_view stands, but published numbers need a quiet machine (see
+# tests/benchmarks/json_view/README.md).
+
+on:
+  pull_request:
+    types: [labeled]
+  workflow_dispatch:
+    inputs:
+      runner:
+        description: "Runner image"
+        type: choice
+        options:
+          - ubuntu-24.04
+          - ubuntu-24.04-arm
+        default: ubuntu-24.04
+      compiler:
+        description: "Compiler"
+        type: choice
+        options:
+          - g++
+          - clang++
+        default: g++
+      native:
+        description: "Compile for the runner's CPU (-march=native)"
+        type: boolean
+        default: false
+      rounds:
+        description: "Rounds of bench_view"
+        type: number
+        default: 30
+
+permissions:
+  contents: read
+
+concurrency:
+  # (the label is part of the group: adding an unrelated label must not cancel a running benchmark)
+  group: json-view-benchmarks-${{ github.workflow }}-${{ github.ref }}-${{ github.event.label.name }}
+  cancel-in-progress: true
+
+jobs:
+  compare:
+    if: github.event_name == 'workflow_dispatch' || github.event.label.name == 'benchmark'
+    strategy:
+      matrix:
+        runner: ${{ fromJSON(github.event_name == 'workflow_dispatch' && format('["{0}"]', inputs.runner) || '["ubuntu-24.04", "ubuntu-24.04-arm"]') }}
+    runs-on: ${{ matrix.runner }}
+    timeout-minutes: 60
+    steps:
+      - name: Harden Runner
+        uses: step-security/harden-runner@ccd8616d44fd3846e67624a50d5aad6d37bf2d25 # v2.22.1
+        with:
+          egress-policy: audit
+
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+
+      - name: Download test data
+        run: |
+          cmake -S . -B build -DJSON_BuildTests=On
+          cmake --build build --target download_test_data
+
+      - name: Run the comparison
+        env:
+          CXX: ${{ inputs.compiler || 'g++' }}
+          CC: ${{ inputs.compiler == 'clang++' && 'clang' || 'gcc' }}
+          ROUNDS: ${{ inputs.rounds || 30 }}
+          NATIVE: ${{ inputs.native && '--native' || '' }}
+        run: python3 tests/benchmarks/json_view/compare.py --data build/test_files --download --rounds "$ROUNDS" $NATIVE
+
+      - name: Summary
+        run: cat tests/benchmarks/json_view/results/*.md >> "$GITHUB_STEP_SUMMARY"
+
+      - uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7.0.2
+        with:
+          name: json_view-benchmarks-${{ matrix.runner }}-${{ inputs.compiler || 'g++' }}
+          path: tests/benchmarks/json_view/results/
@@ -80,6 +80,6 @@ jobs:

      # Upload the results to GitHub's code scanning dashboard.
      - name: "Upload to code-scanning"
-        uses: github/codeql-action/upload-sarif@24c54180a607b1449ed407dd24f251e4e9147c8d # v4.38.3
+        uses: github/codeql-action/upload-sarif@6f2ac81f5cd81fe351a197ba0b00d91d03cd2aee # v4.39.0
        with:
          sarif_file: results.sarif
@@ -65,7 +65,7 @@ jobs:

      # Upload SARIF file generated in previous step
      - name: Upload SARIF file
-        uses: github/codeql-action/upload-sarif@24c54180a607b1449ed407dd24f251e4e9147c8d # v4.38.3
+        uses: github/codeql-action/upload-sarif@6f2ac81f5cd81fe351a197ba0b00d91d03cd2aee # v4.39.0
        with:
          sarif_file: semgrep.sarif
        if: always()
@@ -37,6 +37,7 @@ cc_library(
        "include/nlohmann/detail/input/parser.hpp",
        "include/nlohmann/detail/input/position_t.hpp",
        "include/nlohmann/detail/input/pow5_table.hpp",
+        "include/nlohmann/detail/input/simd_scan.hpp",
        "include/nlohmann/detail/input/string_scan.hpp",
        "include/nlohmann/detail/iterators/internal_iterator.hpp",
        "include/nlohmann/detail/iterators/iter_impl.hpp",
@@ -6,6 +6,7 @@ This file describes the source for supporting files; that is, files that are not
 - [GitHub](#github)
 - [REUSE](#reuse)
 - [Package Managers](#package-managers)
+- [Debugging](#debugging)

 ## Continuous Integration

@@ -289,3 +290,29 @@ The module definition for [Bazel](https://bazel.build)'s [Bzlmod](https://bazel.
 Further documentation:

 - [Bazel modules](https://bazel.build/external/module)
+
+## Debugging
+
+### `nlohmann_json.natvis`
+
+The [Natvis](https://learn.microsoft.com/en-us/visualstudio/debugger/create-custom-views-of-native-objects) file that
+gives `json` values a friendly view in the Visual Studio debugger. The file is generated by
+`tools/generate_natvis/generate_natvis.py` from the template `tools/generate_natvis/nlohmann_json.natvis.j2` and the ABI
+tags and version in `include/nlohmann/detail/abi_macros.hpp`; change the script or the template rather than editing
+the file by hand. The file can be updated by calling
+
+```shell
+make natvis
+```
+
+The "Check amalgamation" workflow fails if the file is out of date.
+
+The file covers the namespace variants with up to two ABI tags. A Natvis file for other configurations can be
+generated with the `--abi-tags` or `--all` options, for example
+`make natvis NATVIS_ARGS="--abi-tags _diag,_dp,_vns --output my_nlohmann_json.natvis"`; see
+[`tools/generate_natvis`](tools/generate_natvis/README.md). With MSVC, CMake adds the file to the `nlohmann_json`
+target and installs it.
+
+Further documentation:
+
+- [Create custom views of C++ objects in the debugger using the Natvis framework](https://learn.microsoft.com/en-us/visualstudio/debugger/create-custom-views-of-native-objects)
@@ -46,7 +46,7 @@ all:
 	@echo "clean - remove built files"
 	@echo "(fuzzers) - see tests/fuzzing.md, or run 'make -C tests fuzzers' to build the AFL fuzzers"
 	@echo "macro_builder_check - check that macro_scope.hpp matches tools/macro_builder's output"
-	@echo "natvis - regenerate nlohmann_json.natvis from the current ABI tags and version"
+	@echo "natvis - regenerate nlohmann_json.natvis from the current ABI tags and version (pass generator options via NATVIS_ARGS, see tools/generate_natvis/README.md)"
 	@echo "pretty - beautify code with Artistic Style"
 	@echo "pvs_studio - run the PVS-Studio static analyzer and open the report"
 	@echo "release - create the release files (include.zip, json.tar.xz, single headers, signatures, hashes)"
@@ -120,13 +120,15 @@ $(AMALGAMATED_VIEW_FILE): $(SRCS)
 	tools/amalgamate/amalgamate.py -c tools/amalgamate/config_json_view.json -s . --verbose=yes

 NATVIS_VENV=tools/generate_natvis/venv
+# extra options for generate_natvis.py, e.g. NATVIS_ARGS="--abi-tags _diag,_dp,_vns --output my.natvis"
+NATVIS_ARGS=

 # regenerate nlohmann_json.natvis from the ABI tags and version in include/nlohmann/detail/abi_macros.hpp
 # (the dependencies are installed into a virtual environment first)
 natvis:
 	@test -d $(NATVIS_VENV) || python3 -mvenv $(NATVIS_VENV)
 	@$(NATVIS_VENV)/bin/python3 -c 'import jinja2' 2>/dev/null || $(NATVIS_VENV)/bin/pip3 install --quiet -r tools/generate_natvis/requirements.txt
-	$(NATVIS_VENV)/bin/python3 tools/generate_natvis/generate_natvis.py .
+	$(NATVIS_VENV)/bin/python3 tools/generate_natvis/generate_natvis.py $(NATVIS_ARGS) .

 # regenerate the two tools/macro_builder blocks of $(MACRO_SCOPE_HPP) (see its README.md) and diff against the
 # checked-in header; phony, because it never writes $(MACRO_SCOPE_HPP) itself
@@ -341,13 +341,14 @@ def download(url, docs) -> str:
        raise ValueError(f'not an http(s) URL: {url}')
    req = urllib.request.Request(u.geturl(), headers={'User-Agent': USER_AGENT})
    # (the scheme is checked above)
+    # nosemgrep: python.lang.security.audit.dynamic-urllib-use-detected.dynamic-urllib-use-detected
    with urllib.request.urlopen(req, timeout=20) as r:  # nosec B310
        data = r.read()
        ctype = r.headers.get_content_type()
    path = urllib.parse.unquote(u.path).lstrip('/')
    ext = os.path.splitext(path)[1]
    if u.query or not ext or path.endswith('/'):
-        digest = hashlib.sha1(url.encode(), usedforsecurity=False).hexdigest()[:12]
+        digest = hashlib.sha256(url.encode()).hexdigest()[:12]
        path = os.path.join(os.path.dirname(path), digest + CONTENT_TYPE_EXT.get(ctype, ext or '.bin'))
    rel = os.path.normpath(os.path.join('assets', 'external', u.hostname, path))
    out = os.path.join(docs, rel)
@@ -80,7 +80,8 @@ None of these exceptions carry a [`JSON_DIAGNOSTICS`](../macros/json_diagnostics
   Objects with 128 or more members get a hash index of their keys while parsing, so that a lookup in them takes
   constant time on average.
 2. Linear in `idx`: elements are skipped one at a time from the first one, since they are not a fixed size in the
-   index (unlike `BasicJsonType`'s array, which is random-access).
+   index (unlike `BasicJsonType`'s array, which is random-access). Constant if no element of the array is an array
+   or object, since the elements are then adjacent in the index.
 3. Linear in the number of reference tokens of `ptr` and, for each token, in the number of members of the object at
   that level (as 1.) or the index into the array (as 2.).

@@ -28,7 +28,8 @@ This exception does not carry a [`JSON_DIAGNOSTICS`](../macros/json_diagnostics.

 Linear in the size of the array or object: unlike [`front()`](front.md), which only ever looks at the first
 element, `back()` has to walk every element to find where they end, since elements are not a fixed size in the
-index.
+index. Constant if no element of the array is an array or object, since the elements are then adjacent
+in the index.

 ## Notes

@@ -86,7 +86,8 @@ None of these exceptions carry a [`JSON_DIAGNOSTICS`](../macros/json_diagnostics
   Objects with 128 or more members get a hash index of their keys while parsing, so that a lookup in them takes
   constant time on average.
 2. Linear in `idx`: elements are skipped one at a time from the first one, since they are not a fixed size in the
-   index (unlike `BasicJsonType`'s array, which is random-access).
+   index (unlike `BasicJsonType`'s array, which is random-access). Constant if no element of the array is an array
+   or object, since the elements are then adjacent in the index.
 3. Linear in the number of reference tokens of `ptr` and, for each token, in the number of members of the object at
   that level (as 1.) or the index into the array (as 2.).

@@ -38,6 +38,7 @@ header. See also the [macro overview page](../../features/macros.md).
 - [**JSON_HAS_THREE_WAY_COMPARISON**](json_has_three_way_comparison.md) - control 3-way comparison support
 - [**JSON_NO_AUTOMATIC_UDLS**](json_no_automatic_udls.md) - do not include the user-defined string literals (UDLs) automatically
 - [**JSON_NO_IO**](json_no_io.md) - switch off functions relying on certain C++ I/O headers
+- [**JSON_NO_SIMD**](json_no_simd.md) - use only portable code instead of vector instructions (SSE2, SSSE3, NEON)
 - [**JSON_NO_THREAD_LOCAL**](json_no_thread_local.md) - switch off the use of `thread_local` storage
 - [**JSON_SKIP_UNSUPPORTED_COMPILER_CHECK**](json_skip_unsupported_compiler_check.md) - do not warn about unsupported compilers
 - [**JSON_USE_GLOBAL_UDLS**](json_use_global_udls.md) - place user-defined string literals (UDLs) into the global namespace
@@ -0,0 +1,83 @@
+# JSON_NO_SIMD
+
+```cpp
+#define JSON_NO_SIMD
+```
+
+When defined, the library uses only portable C++ code where it would otherwise use vector instructions: when scanning
+strings during parsing, and when writing floating-point numbers during serialization.
+
+The macro is an escape hatch, for example for toolchains that cannot compile the vector code, for sanitizers or
+analyzers that do not understand it, or to compare the speed of both variants. It does not change any result: values,
+exceptions, and error positions are the same either way. Only the speed differs.
+
+## Default definition
+
+By default, `#!cpp JSON_NO_SIMD` is not defined, and vector instructions are used where the target has them.
+
+```cpp
+#undef JSON_NO_SIMD
+```
+
+## Notes
+
+!!! note "Which instructions are used"
+
+    - **x86-64:** SSE2, which every x86-64 CPU has, finds the end of runs of plain string characters 16 bytes at a time
+      and writes the digits of floating-point numbers. The UTF-8 check of non-ASCII text needs SSSE3, which is not part
+      of x86-64: it is compiled for SSSE3 with a function attribute and used when the CPU has SSSE3 (every x86-64 CPU
+      since about 2011), else the portable check. Code compiled for SSSE3 anyway (e.g., with `-mssse3` or `-march=native`)
+      skips this check of the CPU. 32-bit x86 uses SSE2 for strings when the compiler targets it.
+    - **AArch64:** NEON, which every 64-bit Arm CPU has, checks UTF-8 text and long runs of plain string characters 16
+      bytes at a time, and writes the digits of floating-point numbers. With MSVC, only the floating-point digits use
+      NEON.
+    - **Other targets:** portable code only.
+
+    Strings are only scanned this way for contiguous input and for the characters a `#!cpp std::istream` holds in its
+    stream buffer (see [`JSON_DISABLE_STREAM_BULK_SCAN`](json_disable_stream_bulk_scan.md)); other inputs are read one
+    character at a time.
+
+!!! note "Interaction with `JSON_USE_SIMDUTF`"
+
+    With [`JSON_USE_SIMDUTF`](json_use_simdutf.md), runs of string characters are first validated by simdutf; the code
+    described here is used for what simdutf does not accept, so that errors are reported at the same position.
+    `JSON_NO_SIMD` does not affect simdutf.
+
+!!! note "ABI compatibility"
+
+    The macro selects between two definitions of the library's internal scanning and formatting functions. Whether it
+    is defined is encoded in the [namespace](../../features/namespace.md) (tag `_ns`), resulting in distinct symbol
+    names. Translation units compiled with and without it can therefore be linked into the same program without One
+    Definition Rule (ODR) violations, but they cannot exchange instances of library types.
+
+## Examples
+
+??? example "Example: switching off vector instructions"
+
+    The program parses and serializes the same values with and without the macro:
+
+    ```cpp
+    #define JSON_NO_SIMD
+    #include <iostream>
+    #include <nlohmann/json.hpp>
+
+    using json = nlohmann::json;
+
+    int main()
+    {
+        const json j = json::parse(R"({"name": "日本語 text", "pi": 3.141592653589793})");
+        std::cout << j.dump() << '\n';  // {"name":"日本語 text","pi":3.141592653589793}
+    }
+    ```
+
+## See also
+
+- [**parse**](../basic_json/parse.md) - deserialize from a compatible input
+- [**dump**](../basic_json/dump.md) - serialization
+- [**JSON_USE_SIMDUTF**](json_use_simdutf.md) - use the simdutf library to accelerate UTF-8 validation
+- [**JSON_DISABLE_STREAM_BULK_SCAN**](json_disable_stream_bulk_scan.md) - read a `std::istream` one character at a time
+- [Parsing: input sources and performance](../../features/parsing/index.md#input-sources-and-performance)
+
+## Version history
+
+- Added in version 3.13.0.
@@ -6,8 +6,9 @@

 When defined, the parser validates the UTF-8 content of JSON strings that come from a **contiguous byte input**
 (`std::string`, `std::vector<char>`/`<std::uint8_t>`, string literals, `const char*` ranges, …) using the
-[simdutf](https://github.com/simdutf/simdutf) library instead of the built-in scalar validator. On text with many
-non-ASCII characters (e.g. CJK or emoji) this can validate several times faster.
+[simdutf](https://github.com/simdutf/simdutf) library instead of the built-in validator (which uses SSSE3 or NEON where
+available, see [`JSON_NO_SIMD`](json_no_simd.md)). On text with many non-ASCII characters (e.g. CJK or emoji) this can
+validate faster, depending on the CPU.

 This is an **opt-in external dependency**. The library itself remains header-only and its behavior is unchanged: the
 same input is accepted or rejected either way, and every parse error is reported at the same position with the same
@@ -39,6 +39,6 @@ the library.
 ## Version history

 - Added in version 3.11.0. Changed inline namespace name in version 3.11.2. Added the ABI tag `_dp` in
-  version 3.12.0, and the ABI tags `_bics`, `_psp`, `_snul`, `_sbu8`, `_ekmo`, `_dsbs`, `_dufio`, `_vns`, and
-  `_vssse3` in version 3.13.0; see
+  version 3.12.0, and the ABI tags `_bics`, `_psp`, `_snul`, `_sbu8`, `_ekmo`, `_dsbs`, `_dufio`, `_ns`, `_vns`,
+  and `_vssse3` in version 3.13.0; see
  [`nlohmann` Namespace](../../features/namespace.md#structure).
@@ -0,0 +1,42 @@
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    json j = json::parse(R"({"name": "Mary", "age": 42})");
+
+    // look up the key, then test the type: neither step throws
+    for (const char* key : {"name", "age", "city"})
+    {
+        const auto it = j.find(key);
+        if (it == j.end())
+        {
+            std::cout << key << ": missing\n";
+        }
+        else if (it->is_string())
+        {
+            std::cout << key << ": string \"" << it->get_ref<const std::string&>() << "\"\n";
+        }
+        else
+        {
+            std::cout << key << ": not a string, but " << it->type_name() << '\n';
+        }
+    }
+
+    // get_ptr returns a null pointer if the value has another type
+    const std::string* name = j["name"].get_ptr<const std::string*>();
+    const std::string* age = j["age"].get_ptr<const std::string*>();
+    std::cout << "get_ptr<string*>: name = " << (name != nullptr) << ", age = " << (age != nullptr) << '\n';
+
+    // value() is NOT exception-free: it throws if the key exists with a different type
+    try
+    {
+        std::cout << j.value("name", 0) << '\n';
+    }
+    catch (const json::type_error& e)
+    {
+        std::cout << e.what() << '\n';
+    }
+}
@@ -0,0 +1,5 @@
+name: string "Mary"
+age: not a string, but number
+city: missing
+get_ptr<string*>: name = 1, age = 0
+[json.exception.type_error.302] type must be number, but is string
@@ -0,0 +1,46 @@
+#include <iostream>
+#include <optional>
+#include <string>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+struct person
+{
+    std::string name;
+    int age;
+};
+
+NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(person, name, age)
+
+// Compile this function with exceptions enabled and call it from code that does not use them.
+std::optional<person> to_person(const json& j)
+{
+    try
+    {
+        return j.get<person>();
+    }
+    catch (const json::exception&)
+    {
+        return std::nullopt;
+    }
+}
+
+int main()
+{
+    const json good = {{"name", "Mary"}, {"age", 42}};
+    const json bad = {{"name", "Mary"}, {"age", "forty-two"}};
+    const json incomplete = {{"name", "Mary"}};
+
+    for (const json& j : {good, bad, incomplete})
+    {
+        if (const auto p = to_person(j))
+        {
+            std::cout << "person: " << p->name << ", " << p->age << '\n';
+        }
+        else
+        {
+            std::cout << "not a person: " << j << '\n';
+        }
+    }
+}
@@ -0,0 +1,3 @@
+person: Mary, 42
+not a person: {"age":"forty-two","name":"Mary"}
+not a person: {"name":"Mary"}
@@ -0,0 +1,28 @@
+#include <cstdint>
+#include <iostream>
+#include <vector>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+// None of the calls below throws, so this example also works with -fno-exceptions.
+int main()
+{
+    const std::string invalid = R"({"name": "Mary", "age": )";
+
+    // parse() with allow_exceptions = false returns a discarded value
+    json j = json::parse(invalid, nullptr, false);
+    std::cout << std::boolalpha << "parse: discarded = " << j.is_discarded() << '\n';
+
+    // accept() only tells whether the input is valid JSON
+    std::cout << "accept: " << json::accept(invalid) << '\n';
+
+    // the binary formats have the same parameter
+    const std::vector<std::uint8_t> truncated_cbor = {0x83, 0x01};
+    json c = json::from_cbor(truncated_cbor, true, false);
+    std::cout << "from_cbor: discarded = " << c.is_discarded() << '\n';
+
+    // valid input is parsed as usual
+    json valid = json::parse(R"({"name": "Mary"})", nullptr, false);
+    std::cout << "valid input: " << valid << '\n';
+}
@@ -0,0 +1,4 @@
+parse: discarded = true
+accept: false
+from_cbor: discarded = true
+valid input: {"name":"Mary"}
@@ -0,0 +1,42 @@
+#include <iostream>
+#include <utility>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+// line and column (both starting at 1) of a byte index in a text
+std::pair<std::size_t, std::size_t> line_column(const std::string& input, std::size_t byte)
+{
+    std::size_t line = 1;
+    std::size_t column = 1;
+    for (std::size_t i = 0; i + 1 < byte && i < input.size(); ++i)
+    {
+        if (input[i] == '\n')
+        {
+            ++line;
+            column = 1;
+        }
+        else
+        {
+            ++column;
+        }
+    }
+    return {line, column};
+}
+
+int main()
+{
+    const std::string input = "{\n  \"a\": 1,\n  \"b\": ]\n}";
+
+    try
+    {
+        const json j = json::parse(input);
+        std::cout << j << '\n';
+    }
+    catch (const json::parse_error& e)
+    {
+        const auto position = line_column(input, e.byte);
+        std::cout << e.what() << '\n';
+        std::cout << "byte " << e.byte << " = line " << position.first << ", column " << position.second << '\n';
+    }
+}
@@ -0,0 +1,2 @@
+[json.exception.parse_error.101] parse error at line 3, column 8: syntax error while parsing value - unexpected ']'; expected '[', '{', or a literal
+byte 20 = line 3, column 8
@@ -0,0 +1,46 @@
+#define JSON_DIAGNOSTIC_POSITIONS 1
+#include <iostream>
+#include <utility>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+// line and column (both starting at 1) of a byte index in a text
+std::pair<std::size_t, std::size_t> line_column(const std::string& input, std::size_t byte)
+{
+    std::size_t line = 1;
+    std::size_t column = 1;
+    for (std::size_t i = 0; i + 1 < byte && i < input.size(); ++i)
+    {
+        if (input[i] == '\n')
+        {
+            ++line;
+            column = 1;
+        }
+        else
+        {
+            ++column;
+        }
+    }
+    return {line, column};
+}
+
+int main()
+{
+    const std::string input = "{\n  \"name\": \"Mary\",\n  \"age\": \"forty-two\"\n}";
+    const json j = json::parse(input); // the input is valid JSON ...
+
+    try
+    {
+        const int age = j["age"]; // ... but the value has the wrong type
+        std::cout << age << '\n';
+    }
+    catch (const json::exception& e)
+    {
+        std::cout << e.what() << '\n';
+
+        // start_pos() is a 0-based index into the input; the helper expects a 1-based byte index
+        const auto position = line_column(input, j["age"].start_pos() + 1);
+        std::cout << "the value starts at line " << position.first << ", column " << position.second << '\n';
+    }
+}
@@ -0,0 +1,2 @@
+[json.exception.type_error.302] (bytes 29-40) type must be number, but is string
+the value starts at line 3, column 10
@@ -0,0 +1,46 @@
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+std::string buffer;
+
+// call for every chunk; returns true and sets `value` once the buffer holds one complete JSON value
+bool push(const std::string& chunk, json& value)
+{
+    buffer += chunk;
+    try
+    {
+        value = json::parse(buffer);
+        buffer.clear();
+        return true;
+    }
+    catch (const json::parse_error& e)
+    {
+        if (e.byte == buffer.size() + 1)
+        {
+            return false; // the input ends prematurely: wait for more data
+        }
+        throw; // a real syntax error
+    }
+}
+
+int main()
+{
+    json value;
+    for (const std::string chunk : {"{\"na", "me\": \"Ma", "ry\", \"l", "ist\": [1, 2", ", 3]}"})
+    {
+        std::cout << "chunk " << chunk << " -> " << (push(chunk, value) ? "complete" : "incomplete") << '\n';
+    }
+    std::cout << value << '\n';
+
+    // a syntax error in the middle is not mistaken for missing data
+    try
+    {
+        push("[1, ]", value);
+    }
+    catch (const json::parse_error& e)
+    {
+        std::cout << e.what() << '\n';
+    }
+}
@@ -0,0 +1,7 @@
+chunk {"na -> incomplete
+chunk me": "Ma -> incomplete
+chunk ry", "l -> incomplete
+chunk ist": [1, 2 -> incomplete
+chunk , 3]} -> complete
+{"list":[1,2,3],"name":"Mary"}
+[json.exception.parse_error.101] parse error at line 1, column 5: syntax error while parsing value - unexpected ']'; expected '[', '{', or a literal
@@ -0,0 +1,23 @@
+#include <iostream>
+#include <sstream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    // a CBOR value followed by other data
+    const std::vector<std::uint8_t> cbor = json::to_cbor(json{1, 2, 3});
+    std::string data(cbor.begin(), cbor.end());
+    data += "TRAILING";
+
+    std::istringstream input(data);
+    json j = json::from_cbor(input, false); // strict = false: stop after the first value
+
+    std::cout << "value: " << j << '\n';
+    std::cout << "bytes used: " << input.tellg() << '\n';
+
+    std::string rest;
+    input >> rest;
+    std::cout << "remaining input: " << rest << '\n';
+}
@@ -0,0 +1,3 @@
+value: [1,2,3]
+bytes used: 4
+remaining input: TRAILING
@@ -0,0 +1,18 @@
+#include <iostream>
+#include <sstream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+int main()
+{
+    std::istringstream input(R"({"a":1} [2,3] 4 "s")");
+
+    // check for the end of the stream before each read, because a read at the end throws
+    json j;
+    while (input >> std::ws && input.peek() != std::char_traits<char>::eof())
+    {
+        input >> j;
+        std::cout << j << '\n';
+    }
+}
@@ -0,0 +1,4 @@
+{"a":1}
+[2,3]
+4
+"s"
@@ -0,0 +1,27 @@
+#include <iostream>
+#include <sstream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+void handle(const json& record)
+{
+    std::cout << "handling " << record << '\n';
+}
+
+int main()
+{
+    std::istringstream file(R"([{"id": 1}, {"id": 2}, {"id": 3}])");
+
+    json result = json::parse(file, [](int depth, json::parse_event_t event, json & record)
+    {
+        if (depth == 1 && event == json::parse_event_t::object_end)
+        {
+            handle(record);
+            return false; // discard the record
+        }
+        return true;
+    });
+
+    std::cout << "result: " << result << '\n';
+}
@@ -0,0 +1,4 @@
+handling {"id":1}
+handling {"id":2}
+handling {"id":3}
+result: []
@@ -0,0 +1,81 @@
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+struct find_id : nlohmann::json_sax<json>
+{
+    bool next_is_id = false;
+    json::number_unsigned_t id = 0;
+
+    bool key(std::string& name) override
+    {
+        next_is_id = (name == "id");
+        return true;
+    }
+
+    bool number_unsigned(json::number_unsigned_t value) override
+    {
+        if (next_is_id)
+        {
+            id = value;
+            return false; // found: stop parsing
+        }
+        return true;
+    }
+
+    bool null() override
+    {
+        return true;
+    }
+    bool boolean(bool /*val*/) override
+    {
+        return true;
+    }
+    bool number_integer(json::number_integer_t /*val*/) override
+    {
+        return true;
+    }
+    bool number_float(json::number_float_t /*val*/, const std::string& /*s*/) override
+    {
+        return true;
+    }
+    bool string(std::string& /*val*/) override
+    {
+        return true;
+    }
+    bool binary(json::binary_t& /*val*/) override
+    {
+        return true;
+    }
+    bool start_object(std::size_t /*elements*/) override
+    {
+        return true;
+    }
+    bool end_object() override
+    {
+        return true;
+    }
+    bool start_array(std::size_t /*elements*/) override
+    {
+        return true;
+    }
+    bool end_array() override
+    {
+        return true;
+    }
+    bool parse_error(std::size_t /*position*/, const std::string& /*last_token*/, const json::exception& /*ex*/) override
+    {
+        return false;
+    }
+};
+
+int main()
+{
+    find_id handler;
+    const bool completed = json::sax_parse(R"({"x": [1, 2, 3], "id": 42, "rest": [4, 5, 6]})", &handler);
+
+    std::cout << std::boolalpha;
+    std::cout << "parse completed: " << completed << '\n';
+    std::cout << "id: " << handler.id << '\n';
+}
@@ -0,0 +1,2 @@
+parse completed: false
+id: 42
@@ -0,0 +1,56 @@
+#include <chrono>
+#include <iostream>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+namespace nlohmann
+{
+template <typename Rep, typename Period>
+struct adl_serializer<std::chrono::duration<Rep, Period>>
+{
+    static void to_json(json& j, const std::chrono::duration<Rep, Period>& d)
+    {
+        j = d.count();
+    }
+
+    static void from_json(const json& j, std::chrono::duration<Rep, Period>& d)
+    {
+        d = std::chrono::duration<Rep, Period>(j.get<Rep>());
+    }
+};
+
+template <typename Duration>
+struct adl_serializer<std::chrono::time_point<std::chrono::system_clock, Duration>>
+{
+    static void to_json(json& j, const std::chrono::time_point<std::chrono::system_clock, Duration>& t)
+    {
+        j = t.time_since_epoch();
+    }
+
+    static void from_json(const json& j, std::chrono::time_point<std::chrono::system_clock, Duration>& t)
+    {
+        t = std::chrono::time_point<std::chrono::system_clock, Duration>(j.get<Duration>());
+    }
+};
+} // namespace nlohmann
+
+int main()
+{
+    using namespace std::chrono;
+
+    std::cout << std::boolalpha;
+
+    // the unit is not part of the JSON value
+    const json timeout = milliseconds(1500);
+    std::cout << "duration: " << timeout << '\n';
+    std::cout << "as milliseconds: " << timeout.get<milliseconds>().count() << '\n';
+
+    // a system_clock time point is the time since the Unix epoch
+    const time_point<system_clock, milliseconds> t(milliseconds(1700000000123));
+    const json stamp = t;
+    std::cout << "time point: " << stamp << '\n';
+
+    const auto back = stamp.get<time_point<system_clock, milliseconds>>();
+    std::cout << "round trip: " << (back == t) << '\n';
+}
@@ -0,0 +1,4 @@
+duration: 1500
+as milliseconds: 1500
+time point: 1700000000123
+round trip: true
@@ -0,0 +1,99 @@
+#include <iostream>
+#include <memory>
+#include <stdexcept>
+#include <vector>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+struct shape
+{
+    virtual ~shape() = default;
+    virtual json serialize() const = 0;
+};
+
+struct circle : shape
+{
+    double radius;
+
+    explicit circle(double r) : radius(r) {}
+
+    json serialize() const override
+    {
+        return {{"type", "circle"}, {"radius", radius}};
+    }
+};
+
+struct rectangle : shape
+{
+    double width;
+    double height;
+
+    rectangle(double w, double h) : width(w), height(h) {}
+
+    json serialize() const override
+    {
+        return {{"type", "rectangle"}, {"width", width}, {"height", height}};
+    }
+};
+
+namespace nlohmann
+{
+template <>
+struct adl_serializer<std::unique_ptr<shape>>
+{
+    static void to_json(json& j, const std::unique_ptr<shape>& p)
+    {
+        j = p ? p->serialize() : json(nullptr);
+    }
+
+    static void from_json(const json& j, std::unique_ptr<shape>& p)
+    {
+        if (j.is_null())
+        {
+            p.reset();
+            return;
+        }
+
+        const auto& type = j.at("type").get_ref<const std::string&>();
+        if (type == "circle")
+        {
+            p = std::make_unique<circle>(j.at("radius").get<double>());
+        }
+        else if (type == "rectangle")
+        {
+            p = std::make_unique<rectangle>(j.at("width").get<double>(), j.at("height").get<double>());
+        }
+        else
+        {
+            throw std::invalid_argument("unknown shape type: " + type);
+        }
+    }
+};
+} // namespace nlohmann
+
+int main()
+{
+    std::vector<std::unique_ptr<shape>> shapes;
+    shapes.push_back(std::make_unique<circle>(1.5));
+    shapes.push_back(std::make_unique<rectangle>(2, 3));
+
+    const json j = shapes;
+    std::cout << j << '\n';
+
+    // reading creates objects of the derived types
+    const auto back = j.get<std::vector<std::unique_ptr<shape>>>();
+    std::cout << std::boolalpha;
+    std::cout << "first is a circle: " << (dynamic_cast<circle*>(back[0].get()) != nullptr) << '\n';
+    std::cout << "second is a rectangle: " << (dynamic_cast<rectangle*>(back[1].get()) != nullptr) << '\n';
+
+    // an unknown type tag is reported
+    try
+    {
+        json{{"type", "star"}}.get<std::unique_ptr<shape>>();
+    }
+    catch (const std::invalid_argument& e)
+    {
+        std::cout << e.what() << '\n';
+    }
+}
@@ -0,0 +1,4 @@
+[{"radius":1.5,"type":"circle"},{"height":3.0,"type":"rectangle","width":2.0}]
+first is a circle: true
+second is a rectangle: true
+unknown shape type: star
@@ -0,0 +1,90 @@
+#include <iostream>
+#include <memory>
+#include <vector>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+namespace nlohmann
+{
+template <typename T>
+struct adl_serializer<std::shared_ptr<T>>
+{
+    static void to_json(json& j, const std::shared_ptr<T>& p)
+    {
+        if (p)
+        {
+            j = *p;
+        }
+        else
+        {
+            j = nullptr;
+        }
+    }
+
+    static void from_json(const json& j, std::shared_ptr<T>& p)
+    {
+        if (j.is_null())
+        {
+            p = nullptr;
+        }
+        else
+        {
+            p = std::make_shared<T>(j.get<typename std::remove_const<T>::type>());
+        }
+    }
+};
+
+template <typename T>
+struct adl_serializer<std::unique_ptr<T>>
+{
+    static void to_json(json& j, const std::unique_ptr<T>& p)
+    {
+        if (p)
+        {
+            j = *p;
+        }
+        else
+        {
+            j = nullptr;
+        }
+    }
+
+    static void from_json(const json& j, std::unique_ptr<T>& p)
+    {
+        if (j.is_null())
+        {
+            p = nullptr;
+        }
+        else
+        {
+            p = std::make_unique<T>(j.get<T>());
+        }
+    }
+};
+} // namespace nlohmann
+
+struct point
+{
+    int x;
+    int y;
+};
+
+NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(point, x, y)
+
+int main()
+{
+    // an empty pointer is written as null
+    const std::vector<std::shared_ptr<point>> points = {std::make_shared<point>(point{1, 2}), nullptr};
+    const json j = points;
+    std::cout << j << '\n';
+
+    // reading allocates new objects
+    const auto back = j.get<std::vector<std::shared_ptr<point>>>();
+    std::cout << back[0]->x << ", " << back[0]->y << ", " << (back[1] == nullptr) << '\n';
+
+    // pointers to const and unique_ptr work as well
+    const auto const_ptr = j[0].get<std::shared_ptr<const point>>();
+    const auto unique = j[0].get<std::unique_ptr<point>>();
+    std::cout << const_ptr->y << ", " << unique->x << '\n';
+}
@@ -0,0 +1,3 @@
+[{"x":1,"y":2},null]
+1, 2, 1
+2, 1
@@ -0,0 +1,63 @@
+#include <iostream>
+#include <stdexcept>
+#include <variant>
+#include <vector>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+namespace geo
+{
+struct circ
+{
+    double radius;
+};
+
+struct rect
+{
+    double width;
+    double height;
+};
+
+NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(circ, radius)
+NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(rect, width, height)
+
+using figure = std::variant<circ, rect>;
+
+void to_json(json& j, const figure& f)
+{
+    std::visit([&j](const auto & alternative)
+    {
+        j = alternative;
+    }, f);
+    j["type"] = std::holds_alternative<circ>(f) ? "circ" : "rect";
+}
+
+void from_json(const json& j, figure& f)
+{
+    const auto& type = j.at("type").get_ref<const std::string&>();
+    if (type == "circ")
+    {
+        f = j.get<circ>();
+    }
+    else if (type == "rect")
+    {
+        f = j.get<rect>();
+    }
+    else
+    {
+        throw std::invalid_argument("unknown figure type: " + type);
+    }
+}
+} // namespace geo
+
+int main()
+{
+    const std::vector<geo::figure> figures = {geo::circ{2}, geo::rect{3, 4}};
+
+    const json j = figures;
+    std::cout << j << '\n';
+
+    const auto back = j.get<std::vector<geo::figure>>();
+    std::cout << "alternatives read back: " << back[0].index() << ", " << back[1].index() << '\n';
+}
@@ -0,0 +1,2 @@
+[{"radius":2.0,"type":"circ"},{"height":4.0,"type":"rect","width":3.0}]
+alternatives read back: 0, 1
@@ -409,6 +409,32 @@ namespace nlohmann {
 }
 ```

+## Why isn't my `to_json` or `from_json` found?
+
+The library calls `to_json` and `from_json` without qualification, so the compiler finds them by
+[argument-dependent lookup](https://en.cppreference.com/w/cpp/language/adl) in the namespace of the type, or in the
+namespaces of its template arguments. The usual reasons for a function that is "not found" are:
+
+- **The type is an alias of a standard type.** After `#!cpp using Hash = std::array<std::uint8_t, 6>;` the type
+  *is* `std::array<std::uint8_t, 6>`, which lives in namespace `std`. A `to_json(json&, const Hash&)` in your namespace
+  is never selected. Either give the type its own identity, for example `#!cpp struct Hash : std::array<std::uint8_t, 6> {};`
+  (the function is then found in `Hash`'s namespace), or specialize
+  [`adl_serializer<Hash>`](#how-do-i-convert-third-party-types).
+- **The function is in the wrong namespace.** It must be in the namespace of the type (a global type needs a global
+  function), not in the namespace of the code that calls the conversion. Specializations of `adl_serializer` belong in
+  namespace `nlohmann`.
+- **It is declared too late.** A conversion can only use what has been declared when it is instantiated. If
+  `#!cpp json j = std::vector<third_party::string>{...};` appears before the `adl_serializer` specialization, the
+  compiler reports an error such as "explicit specialization of `adl_serializer<...>` after instantiation". Put the
+  specialization in a small header that every file includes **before** it uses the type with `json`.
+- **It is a template.** For `template <class T> struct box`, write `template <class T> void to_json(json&, const box<T>&)`,
+  not an overload for one `T`.
+- **It worked by accident.** Some versions found `to_json` overloads in `nlohmann::detail` through argument-dependent
+  lookup of the base class of `basic_json`. Do not rely on this; it is not part of the interface.
+
+For smart pointers, class hierarchies, `std::variant`, and `std::chrono`, see
+[Recipes for common types](type_recipes.md).
+
 ## Why can't I convert to/from `std::any`?

 `std::any` is intentionally excluded from `get<T>()`/generic conversion support, so `get<std::any>()` and
@@ -505,6 +531,7 @@ struct bad_serializer

 ## See also

+- [Recipes for common types](type_recipes.md) - smart pointers, class hierarchies, `std::variant`, and `std::chrono`
 - [Converting values](conversions.md) - the general overview of `get`/`get_to` and implicit conversions
 - [Specializing enum conversion](enum_conversion.md) - map enums to JSON strings instead of integers
 - [Supported macros](macros.md) - reference for `NLOHMANN_DEFINE_TYPE_*` and related macros
@@ -7,7 +7,9 @@ detect bugs in client code.
 ## Switch off runtime assertions

 Runtime assertions can be switched off by defining the preprocessor macro `NDEBUG` (see the
-[documentation of assert](https://en.cppreference.com/w/cpp/error/assert)) which is the default for release builds.
+[documentation of assert](https://en.cppreference.com/w/cpp/error/assert)) which is the default for release builds. Without `NDEBUG`, the assertions are compiled in and contain the name of the source
+file (`__FILE__`); see [notes for builds and distribution](../integration/index.md#notes-for-builds-and-distribution)
+if that path must not end up in your binaries.

 ## Change assertion behavior

@@ -112,6 +112,29 @@ Implicit conversions are convenient but can be surprising (for example, in overl
 be disabled by defining [`JSON_USE_IMPLICIT_CONVERSIONS`](../api/macros/json_use_implicit_conversions.md) to `#!cpp 0`,
 which forces the explicit `get` form and can catch unintended conversions at compile time.

+!!! warning "`auto` copies the JSON value; it does not convert it"
+
+    The type of `#!cpp j["name"]` is `json`, not the C++ type of the value inside. `#!cpp auto` therefore deduces
+    `json`:
+
+    ```cpp
+    json j = {{"name", "Mary"}, {"age", 42}};
+
+    auto name = j["name"];                       // json: a copy of the value; prints as "Mary" (with quotes)
+    std::string s1 = j["name"];                  // std::string: implicit conversion
+    auto s2 = j["name"].get<std::string>();      // std::string: explicit conversion
+    auto& age = j["age"];                        // json&: a reference, no copy
+    age = 43;                                    // changes j
+    ```
+
+    This is also why `#!cpp std::cout << j["name"]` prints the quotes (see
+    [getting a string without quotes](#getting-values-out)), and why a `json` value cannot be passed to `printf`: the
+    argument is not an `int` or a `char*`, and a compiler either rejects passing it through `...` (Clang does) or
+    compiles it and prints garbage. Convert first: `#!cpp std::printf("%d", j["age"].get<int>());`.
+
+    Prefer `get<T>()` over `auto` when you want the C++ value, and `auto&` or `const auto&` when you want to avoid a
+    copy of a large value.
+
 !!! warning "Conversions do not range-check numbers"

    Just like C++ itself, the `get` family performs numeric conversions without range checks — retrieving a
@@ -59,6 +59,25 @@ with a string as the first element is treated as an object, everything else as a
    [FAQ](../home/faq.md#brace-initialization-yields-arrays) for details and the opt-in
    [`JSON_BRACE_INIT_COPY_SEMANTICS`](../api/macros/json_brace_init_copy_semantics.md) macro.

+### What does this produce?
+
+The following table shows how some common spellings are interpreted. When in doubt, use `#!cpp json::array()`,
+`#!cpp json::object()`, or the `#!cpp json(value)` form with parentheses.
+
+| code                                            | result                       | note                                         |
+|-------------------------------------------------|------------------------------|----------------------------------------------|
+| `#!cpp json j = {};` / `#!cpp json j{};`        | `#!json null`                | use `json::object()` or `json::array()`      |
+| `#!cpp json j = json::object();`                | `#!json {}`                  |                                              |
+| `#!cpp json j = json::array();`                 | `#!json []`                  |                                              |
+| `#!cpp json j(true);`                           | `#!json true`                | parentheses create the value itself          |
+| `#!cpp json j = {true};`                        | `#!json [true]`              | braces create a one-element array (`#!cpp json j{true};` depends on the compiler, see the [FAQ](../home/faq.md#brace-initialization-yields-arrays)) |
+| `#!cpp json j = {{"a", 1}};`                    | `#!json {"a":1}`             | all elements are `[string, value]` pairs: object |
+| `#!cpp json j = {{"a", 1}, {"b"}};`             | `#!json [["a",1],["b"]]`     | one element is not a pair: array             |
+| `#!cpp json j = {{"a", 1}, 2};`                 | `#!json [["a",1],2]`         | a plain value among pairs: array             |
+| `#!cpp json j = {{"a", 1, 2}};`                 | `#!json [["a",1,2]]`         | a three-element list is not a pair: array    |
+| `#!cpp json j = "{\"a\":1}";`                   | `#!json "{\"a\":1}"`           | a string **value**; it is not parsed         |
+| `#!cpp json j = json::parse("{\"a\":1}");`      | `#!json {"a":1}`             | parse text with `parse` or `_json`           |
+
 ## Building incrementally

 A value can also be built up piece by piece. Accessing a non-existing object key or array index with
@@ -21,3 +21,42 @@ flowchart TD
    A --> F{"just testing first?"}
    F -->|"yes"| G["contains() / find()"]
 ```
+
+## Does this key exist?
+
+Use [`contains`](../../api/basic_json/contains.md) to test for a key; it does not modify the value and does not throw:
+
+```cpp
+json j = {{"name", "Mary"}, {"address", {{"city", "Berlin"}}}};
+
+j.contains("name");                   // true
+j.contains("age");                    // false
+j.contains("city");                   // false: contains() only looks at the top level
+j["address"].contains("city");        // true
+j.contains(json::json_pointer("/address/city"));  // true: a JSON pointer tests a nested path in one call
+```
+
+If the value is needed afterwards, [`find`](../../api/basic_json/find.md) tests and accesses with a single lookup:
+
+```cpp
+if (auto it = j.find("name"); it != j.end())
+{
+    std::cout << *it << '\n';
+}
+```
+
+`contains` also returns `true` for a key whose value is `null`; use `j.contains("k") && !j["k"].is_null()` if a
+`null` should count as missing. To read a value with a fallback instead, see [`value`](default_value.md).
+
+!!! warning "`operator[]` inserts missing keys"
+
+    Like `#!cpp std::map::operator[]`, the non-const [`operator[]`](unchecked_access.md) adds a `null` value if the key
+    is missing. Testing a key with it therefore *changes the object*:
+
+    ```cpp
+    json j = {{"foo", 1}};
+    bool absent = j["bar"].is_null();   // true, but j is now {"bar": null, "foo": 1}
+    ```
+
+    Use `contains`/`find` to test, and [`at`](checked_access.md) to access a value that must exist (it throws an
+    [`out_of_range`](../../home/exceptions.md#out-of-range) exception otherwise).
@@ -174,6 +174,13 @@ security reasons (e.g., Intel Software Guard Extensions (SGX)).

 See [full documentation of `JSON_NO_IO`](../api/macros/json_no_io.md).

+## `JSON_NO_SIMD`
+
+When defined, the library uses only portable code instead of vector instructions (SSE2, SSSE3, NEON) for scanning
+strings and writing floating-point numbers. Results are the same either way. It is not defined by default.
+
+See [full documentation of `JSON_NO_SIMD`](../api/macros/json_no_simd.md).
+
 ## `JSON_NO_THREAD_LOCAL`

 When defined, the library does not use `#!cpp thread_local` storage. Copying a value and comparing two values then
@@ -27,6 +27,7 @@ The complete default namespace name is derived as follows:
      `_dsbs`.
    - [`JSON_DISABLE_UNLOCKED_FILE_IO`](../api/macros/json_disable_unlocked_file_io.md) defined non-zero appends
      `_dufio`.
+    - [`JSON_NO_SIMD`](../api/macros/json_no_simd.md) defined appends `_ns`.
    - [`JSON_VIEW_NO_SIMD`](../api/macros/json_view_no_simd.md) defined appends `_vns`.
    - [`JSON_VIEW_USE_SSSE3`](../api/macros/json_view_use_ssse3.md) defined appends `_vssse3`.
 - The inline namespace ends with the suffix `_v` followed by the 3 components of the version number separated by
@@ -114,6 +115,7 @@ follows:
  ([`JSON_STRICT_BINARY_UTF8`](../api/macros/json_strict_binary_utf8.md)), `_ekmo`
  ([`JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS`](../api/macros/json_use_objects_for_enum_keyed_maps.md)), `_dsbs`
  ([`JSON_DISABLE_STREAM_BULK_SCAN`](../api/macros/json_disable_stream_bulk_scan.md)), `_dufio`
-  ([`JSON_DISABLE_UNLOCKED_FILE_IO`](../api/macros/json_disable_unlocked_file_io.md)), `_vns`
+  ([`JSON_DISABLE_UNLOCKED_FILE_IO`](../api/macros/json_disable_unlocked_file_io.md)), `_ns`
+  ([`JSON_NO_SIMD`](../api/macros/json_no_simd.md)), `_vns`
  ([`JSON_VIEW_NO_SIMD`](../api/macros/json_view_no_simd.md)), and `_vssse3`
  ([`JSON_VIEW_USE_SSSE3`](../api/macros/json_view_use_ssse3.md)) in version 3.13.0.
@@ -0,0 +1,113 @@
+# Working Without Exceptions
+
+By default, the library reports errors by throwing exceptions (see [Exceptions](../home/exceptions.md)). This page
+collects what to use when exceptions are unwanted or unavailable, for example in embedded systems, game engines, or
+code compiled with `-fno-exceptions`.
+
+## Two different questions
+
+1. **Can my code avoid *catching* exceptions?** Yes. For parsing and for accessing values there are functions that
+   report failure through a return value. They work in a normal build and need no `#!cpp try`/`#!cpp catch`.
+2. **Can the library be *compiled* without exceptions?** Yes, with `-fno-exceptions` or by defining
+   [`JSON_NOEXCEPTION`](../api/macros/json_noexception.md). Both have the same effect: every `#!cpp throw` in the
+   library becomes a call to `std::abort()`. The functions listed below never reach a `#!cpp throw` for the failures
+   they report, so they keep working in this configuration. Anything else that fails aborts the program.
+
+## Parsing
+
+| function                                                                                    | on invalid input                                    |
+|---------------------------------------------------------------------------------------------|-----------------------------------------------------|
+| `#!cpp json::parse(input, nullptr, false)`                                                  | returns a *discarded* value; test with `is_discarded()` |
+| [`accept`](../api/basic_json/accept.md)                                                     | returns `#!cpp false`                               |
+| `#!cpp json::from_cbor(input, true, false)` (and the other `from_*` functions)              | returns a *discarded* value                         |
+| [`sax_parse`](../api/basic_json/sax_parse.md) with your own handler                         | returns `#!cpp false` after calling `parse_error`   |
+
+??? example "Example: parse and validate without exceptions"
+
+    ```cpp
+    --8<-- "examples/no_exceptions_parse.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/no_exceptions_parse.output"
+    ```
+
+None of the calls in this example throws, so it also compiles and runs with `-fno-exceptions`.
+
+The discarded value carries no message. If you need the position or the reason, use the SAX interface; see
+[Parsing and exceptions](parsing/parse_exceptions.md).
+
+## Accessing values
+
+The access functions are not equally safe. Only some of them never throw:
+
+| expression                          | if the key is missing or the type is wrong                                    |
+|-------------------------------------|-------------------------------------------------------------------------------|
+| `#!cpp j.contains("k")`             | returns `#!cpp false` for a missing key; never throws                         |
+| `#!cpp j.find("k")`                 | returns `end()` for a missing key; never throws                               |
+| `#!cpp j.is_string()`, ...          | the `is_*` functions test the type; never throw                               |
+| `#!cpp j.get_ptr<const std::string*>()` | returns `#!cpp nullptr` for a different type; never throws                |
+| `#!cpp j.at("k")`                   | throws `out_of_range.403` for a missing key                                   |
+| `#!cpp j.get<int>()`                | throws `type_error.302` for a value that is not a number                      |
+| `#!cpp j.value("k", 0)`             | returns the default for a missing key, but **throws `type_error.302` if `k` exists with another type** |
+| `#!cpp j["k"]` (non-const)          | inserts `null` for a missing key                                              |
+| `#!cpp j["k"]` (const)              | undefined behavior for a missing key                                          |
+
+So reading a value that may be absent or of the wrong type without exceptions takes two steps: look up, then test the
+type.
+
+??? example "Example: look up a key and test its type"
+
+    ```cpp
+    --8<-- "examples/no_exceptions_access.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/no_exceptions_access.output"
+    ```
+
+The last lines of the example show why `value` is not on the safe list: it returns the default only for a *missing*
+key.
+
+For numbers, test with `is_number()` (or `is_number_integer()`, `is_number_unsigned()`, `is_number_float()`) before
+calling `get<int>()`, and see [number handling](types/number_handling.md) for range and precision. Whether a value
+fits into the target type is not checked by `get`.
+
+## Converting to your own types
+
+`from_json` functions (including the ones generated by the
+[`NLOHMANN_DEFINE_TYPE_*` macros](arbitrary_types.md#simplify-your-life-with-macros)) report problems by throwing.
+There is no variant that returns an error code. Without exceptions you have two options:
+
+- Validate the JSON value yourself, as shown above, and fill your struct field by field.
+- Convert in a function that is compiled **with** exceptions enabled and catches them at the boundary, returning
+  `std::optional` or an error code to the rest of your code:
+
+??? example "Example: convert to a struct and report failure as std::optional"
+
+    ```cpp
+    --8<-- "examples/no_exceptions_convert.c++17.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/no_exceptions_convert.c++17.output"
+    ```
+
+## Overriding what happens instead of an exception
+
+With exceptions off, you can replace the `abort()` by your own code, for example to log the message first. See
+[Switch off exceptions](../home/exceptions.md#switch-off-exceptions) and
+[`JSON_THROW_USER`](../api/macros/json_throw_user.md). The handler must not return normally.
+
+## See also
+
+- [Exceptions](../home/exceptions.md) - all exceptions and their ids
+- [Parsing and exceptions](parsing/parse_exceptions.md) - the parsing alternatives in detail
+- [Parsing untrusted input](parsing/untrusted_input.md)
+- [`JSON_NOEXCEPTION`](../api/macros/json_noexception.md)
@@ -33,7 +33,9 @@ json data = json::parse(f);
 ```

 The input must be encoded in UTF-8; other encodings are not supported. A single input may contain only one JSON value.
-Inputs consisting of multiple values separated by newlines are handled by the [JSON Lines](json_lines.md) format.
+Inputs consisting of multiple values separated by newlines are handled by the [JSON Lines](json_lines.md) format; input
+that arrives in chunks or contains several values is covered in
+[Large, streamed, and partial input](large_and_partial_input.md).

 By default, the library rejects comments and trailing commas. Both can be enabled with parameters of the `parse`
 function — see [comments](../comments.md) and [trailing commas](../trailing_commas.md).
@@ -79,9 +81,13 @@ follow the usual `std::streambuf` contract, and
 [`JSON_DISABLE_UNLOCKED_FILE_IO`](../../api/macros/json_disable_unlocked_file_io.md) for programs in which another
 thread must use the same `#!cpp FILE` object while it is parsed.

+Where the target has them, strings are scanned with vector instructions: SSE2 on x86-64 (and SSSE3 for UTF-8 text, when
+the CPU has it) and NEON on AArch64. [`JSON_NO_SIMD`](../../api/macros/json_no_simd.md) selects portable code instead,
+again without changing any result.
+
 ## SAX vs. DOM parsing

-The library offers two parsing models:
+The library offers two parsing models, and a third, read-only alternative:

 - **DOM parsing** (the default): the complete input is read and stored as an in-memory `basic_json` value that can be
  traversed and modified freely. This is what [`parse`](../../api/basic_json/parse.md) does, and it is the right choice
@@ -91,6 +97,13 @@ The library offers two parsing models:
  inputs or when you only need to extract parts of the input. See the [SAX interface](sax_interface.md) for details and
  [`sax_parse`](../../api/basic_json/sax_parse.md) for the API.

+- **Document and views** (`#!cpp <nlohmann/json_view.hpp>`, added in version 3.13.0): [`json_document::parse`](../../api/basic_json_document/parse.md)
+  reads the same JSON grammar but builds a flat, read-only index of the values instead of a `basic_json` tree. Strings and
+  floating-point numbers are read from the text on demand, and only the parts you
+  [`materialize()`](../../api/basic_json_view/materialize.md) become `basic_json` values. This avoids most of the work when you
+  need only a few values from a large or frequently parsed text; see [Zero-copy JSON views](../json_view.md). It is read-only, so use
+  `parse` when you need to modify the value.
+
 You can influence a DOM parse without switching to the SAX interface by passing a
 [parser callback](parser_callbacks.md), which is called during parsing and can, for example, discard parts of the input.

@@ -107,7 +120,9 @@ options.
 - [`accept`](../../api/basic_json/accept.md) - check if the input is valid JSON
 - [`sax_parse`](../../api/basic_json/sax_parse.md) - generate SAX events
 - [JSON Lines](json_lines.md) - parse newline-delimited JSON
+- [Large, streamed, and partial input](large_and_partial_input.md) - chunked, concatenated, and very large input
 - [parser callbacks](parser_callbacks.md) - influence the parsing by a callback function
 - [SAX interface](sax_interface.md) - implement a custom SAX handler
+- [Zero-copy JSON views](../json_view.md) - parse into a read-only document and read it through views
 - [parsing and exceptions](parse_exceptions.md) - control error handling
 - [parsing untrusted input](untrusted_input.md) - what to consider when parsing input from untrusted sources
@@ -0,0 +1,154 @@
+# Large, Streamed, and Partial Input
+
+[`parse`](../../api/basic_json/parse.md) reads exactly one complete JSON value and builds it in memory. It cannot be
+paused and resumed, and it does not hand back a half-parsed value when the input ends early. This page shows what to do
+when the input does not fit that model: it arrives in pieces, it contains several values, or it is too large to hold
+as a `json` value.
+
+```mermaid
+flowchart TD
+    A["my input is..."] --> B{"several JSON values in one stream?"}
+    B -->|"yes"| C["read them one at a time"]
+    A --> D{"arriving in chunks (socket, pipe)?"}
+    D -->|"yes"| E["frame the messages, or buffer until complete"]
+    A --> F{"too large to keep in memory?"}
+    F -->|"yes"| G["discard parts with a callback, or use SAX"]
+    A --> H{"only a small part is needed?"}
+    H -->|"yes"| I["stop early with SAX, or read through a view"]
+```
+
+## Several values in one stream
+
+For newline-delimited input, read line by line and parse each line, as described in [JSON Lines](json_lines.md). For
+values that are simply concatenated, [`operator>>`](../../api/operator_gtgt.md) reads one value and leaves the stream
+positioned after it. Check for the end of the stream before each read, because a read at the end throws:
+
+??? example "Example: read concatenated values"
+
+    ```cpp
+    --8<-- "examples/partial_input_concatenated.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/partial_input_concatenated.output"
+    ```
+
+The same works for binary formats. [`from_cbor`](../../api/basic_json/from_cbor.md) and its relatives accept
+`#!cpp strict = false` to stop after the first value and leave the rest of the stream untouched; `tellg()` then reports
+how many bytes the value took:
+
+??? example "Example: read one CBOR value and find out how many bytes it used"
+
+    ```cpp
+    --8<-- "examples/partial_input_cbor.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/partial_input_cbor.output"
+    ```
+
+## Input arriving in chunks
+
+A socket, pipe, or HTTP body hands over data in pieces of arbitrary size, and a piece can end in the middle of a
+number, a string, or an object. The parser does not keep state between calls, so there are two ways to deal with this.
+
+**Frame the messages.** The most robust approach is a protocol that says where a value ends: one value per line
+([JSON Lines](json_lines.md)), a length prefix, or a delimiter. Collect the bytes of one message and parse them when
+the frame is complete. Prefer this whenever you control the protocol.
+
+**Buffer until the value is complete.** If the data has no framing, append every chunk to a buffer and try to parse
+it. A parse error at the very end of the buffer means that the input ended prematurely, while an error anywhere else is
+a real syntax error. The member `byte` of the [`parse_error`](../../home/exceptions.md#jsonexceptionparse_error101)
+exception is one past the buffer size in the first case:
+
+??? example "Example: buffer chunks until the value is complete"
+
+    ```cpp
+    --8<-- "examples/partial_input_buffering.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/partial_input_buffering.output"
+    ```
+
+The example feeds a document in five chunks. The first four are reported as incomplete, and a syntax error is reported as
+such, not as missing data.
+
+!!! warning "Limits of buffering"
+
+    - The buffer must contain exactly one value. Data that belongs to the next value is a syntax error. Use framing if
+      values follow each other without a separator.
+    - A number at the end of the buffer is a complete value, even if more digits are still to come (`12` may be the
+      start of `123`). Buffering cannot detect this; use framing for top-level numbers.
+    - Every attempt parses the buffer from the beginning, so the total work grows quadratically with the size of the
+      value. Limit the size of the buffer for input you do not trust (see [untrusted input](untrusted_input.md)).
+
+## Input too large for memory
+
+The input does not have to become one huge `json` value. The two tools below process it piece by piece.
+
+### Handle and discard elements with a callback
+
+A [parser callback](parser_callbacks.md) is called for every finished value. If it returns `#!cpp false`, the value is
+discarded and its memory is released at once. For a file that consists of one huge array (or one huge object) of
+records, handle each record at depth 1 and discard it:
+
+??? example "Example: handle and discard each record of a large array"
+
+    ```cpp
+    --8<-- "examples/partial_input_discard_records.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/partial_input_discard_records.output"
+    ```
+
+Only one record is in memory at any time. The same recipe, with more detail, is in the
+[parser callbacks](parser_callbacks.md#recipe-streaming-a-large-homogeneous-array) page. To skip entire members you do not
+need, discard them when their key is read; see the [example](parser_callbacks.md) for `parse_event_t::key`.
+
+### Extract a few values and stop with SAX
+
+With the [SAX interface](sax_interface.md), no value is built at all, and **returning `#!cpp false` from any handler
+function stops the parser**. [`sax_parse`](../../api/basic_json/sax_parse.md) then returns `#!cpp false`, and the rest
+of the input is not read. The example finds the first `id` in a document without parsing the remainder:
+
+??? example "Example: stop parsing as soon as a value is found"
+
+    ```cpp
+    --8<-- "examples/partial_input_sax_stop.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/partial_input_sax_stop.output"
+    ```
+
+Note that `sax_parse` returns `#!cpp false` both when a handler stopped the parse and when the input is invalid, so
+record the reason in the handler (here: `id`) if you need to tell the two apart.
+
+### Read parts of a large document with a view
+
+If the whole text is available and you only need to read some of it, a [`json_document`](../json_view.md) from
+`<nlohmann/json_view.hpp>` (added in version 3.13.0) avoids the `basic_json` tree altogether: it keeps the text, builds a flat index of the values,
+and gives read-only [views](../../api/basic_json_view/index.md) of the parts you look at. Only what you
+[`materialize()`](../../api/basic_json_view/materialize.md) becomes a `basic_json` value. See
+[Zero-copy JSON views](../json_view.md) for details and for the lifetime rules.
+
+## See also
+
+- [Parsing](index.md) - overview of the parsing functions
+- [JSON Lines](json_lines.md) - newline-delimited JSON
+- [Parser callbacks](parser_callbacks.md) - discard values while parsing
+- [SAX interface](sax_interface.md) - event-based parsing
+- [Zero-copy JSON views](../json_view.md) - read parts of a large document without building a tree
+- [Untrusted input](untrusted_input.md) - limits for input you do not control
@@ -21,6 +21,10 @@ catch (json::parse_error& ex)
 In case exceptions are undesired or not supported by the environment, there are different ways to proceed:


+!!! tip
+
+    [Working without exceptions](../no_exceptions.md) also covers accessing values and converting to your own types.
+
 ## Switch off exceptions

 The [`parse()`](../../api/basic_json/parse.md) function accepts a `#!cpp bool` parameter `allow_exceptions` which
@@ -81,3 +85,61 @@ The return value indicates whether the parsing should continue, so the function
    ```
    --8<-- "examples/sax_no_exception.output"
    ```
+
+## Where did the error occur?
+
+The message of a [`parse_error`](../../home/exceptions.md#jsonexceptionparse_error101) for JSON text contains the line
+and column of the error:
+
+```
+[json.exception.parse_error.101] parse error at line 3, column 8: syntax error while parsing value - unexpected ']'; expected '[', '{', or a literal
+```
+
+The exception object itself only stores the **byte index** of the last read character in the member `byte` (the first
+byte of the input has index 1). The same index is passed to `parse_error` in the [SAX interface](sax_interface.md). If
+you need the line and column as numbers, for example to show them in an editor, compute them from the input:
+
+??? example "Example: compute line and column of a parse error"
+
+    ```cpp
+    --8<-- "examples/parse_error_position.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/parse_error_position.output"
+    ```
+
+Columns count bytes, so a line with multi-byte UTF-8 characters before the error may differ from the column your editor
+shows.
+
+### Where is the value that caused a later error?
+
+A `parse_error` is raised while the text is read. Many mistakes show up later: the text is valid JSON, but a value has
+the wrong type when you convert it (`type_error.302`), or a key is missing (`out_of_range.403`). The exception then says
+what is wrong, but not where in the input the value was. Define
+[`JSON_DIAGNOSTIC_POSITIONS`](../../api/macros/json_diagnostic_positions.md) before including the library to add the
+byte range of the offending value to such messages (since version 3.12.0), and to query the range of any value with
+[`start_pos()`](../../api/basic_json/start_pos.md) and [`end_pos()`](../../api/basic_json/end_pos.md):
+
+??? example "Example: locate a value with diagnostic positions"
+
+    ```cpp
+    --8<-- "examples/parse_error_position_diagnostic.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/parse_error_position_diagnostic.output"
+    ```
+
+Positions are only available for values created by [`parse`](../../api/basic_json/parse.md), they are not updated when a
+value is changed, and the macro makes every value 16 bytes larger on 64-bit platforms, so use it where the cost is
+acceptable, for example for configuration files. Note that `start_pos()` is a 0-based index into the input, whereas
+`byte` of a `parse_error` starts at 1.
+
+For binary formats such as CBOR, there are no lines; `byte` is the position in the byte sequence. To find out how many
+bytes a successfully parsed value used, see
+[Several values in one stream](large_and_partial_input.md#several-values-in-one-stream).
@@ -26,9 +26,11 @@ several alternatives; see [Parsing and exceptions](parse_exceptions.md) for the
  [example](parse_exceptions.md#user-defined-sax-interface) that overrides it to print instead of throw.

 If exceptions are unavailable entirely (`-fno-exceptions`, or [`JSON_NOEXCEPTION`](../../api/macros/json_noexception.md)
-defined), every `#!cpp throw` in the library becomes a call to `std::abort()` -- there is no way to recover from a
-parse error of untrusted input in that configuration; see
-[Switch off exceptions](../../home/exceptions.md#switch-off-exceptions) for the details and for overriding this with
+defined), every `#!cpp throw` in the library becomes a call to `std::abort()`. The alternatives above do not throw, so
+`parse()` with `allow_exceptions` set to `#!cpp false` (and likewise `accept()` and the `from_*` functions with
+`allow_exceptions` set to `#!cpp false`) can still reject invalid input in that configuration; a plain `parse()` call
+aborts on invalid input. See [Working without exceptions](../no_exceptions.md) and
+[Switch off exceptions](../../home/exceptions.md#switch-off-exceptions) for the details and for overriding the abort with
 `JSON_THROW_USER`.

 ## Nesting depth
@@ -20,32 +20,39 @@ below apply on every supported standard. This adapter exposes two optimizations

 - it can reconstruct already-consumed input on demand for error messages, instead of copying every character as it is
  read, and
- the lexer can scan ordinary string characters directly out of the buffer, several bytes at a time, rather than one
-  character (and one function call) at a time.
+- the lexer can scan ordinary string characters, numbers, and indentation directly out of the buffer, several bytes at
+  a time, rather than one character (and one function call) at a time.

-A `#!cpp std::istream` (including `#!cpp std::ifstream`) or `#!cpp FILE*`, by contrast, is read through
-`input_stream_adapter` or `file_input_adapter`, which read one character (or one block, for binary formats) at a time
-and expose neither optimization -- the lexer falls back to the same byte-at-a-time path it uses for any
-non-contiguous, general-purpose iterator range. An iterator pair over non-contiguous but random-access storage (e.g.
-`#!cpp std::deque<char>::iterator`) gets the first optimization but not the second, since the byte-scanning fast path
-additionally requires contiguous storage.
+A `#!cpp std::istream` (including `#!cpp std::ifstream`) gets the same bulk scanning: `input_stream_adapter` scans the
+characters its stream buffer already holds (the *get area*) and asks the stream buffer for more only when they are used
+up. Nothing is read ahead, so the stream is left exactly where it would be after reading one character at a time, and
+[`operator>>`](../api/operator_gtgt.md) can still read several values from one stream. A stream buffer without a get
+area is read one character at a time. A `#!cpp FILE*` is still read one character at a time, but `file_input_adapter`
+locks the file once per parse instead of once per character. See
+[input sources and performance](parsing/index.md#input-sources-and-performance) for the full table. According to the
+description of [#5828](https://github.com/nlohmann/json/pull/5828), parsing from a stream is within about 10 to 20 % of
+parsing an equivalent `#!cpp std::string`.

-Practically: if the JSON text is already in memory, or small enough to read into memory, prefer passing a
-`#!cpp std::string`, a `#!cpp std::vector<char>`, or a pointer range to `parse` over a `#!cpp std::istream`. For a
-file, that means reading it into a string first and then parsing the string, rather than passing a
-`#!cpp std::ifstream` directly to `parse` -- the latter never benefits from either optimization:
+Inputs that are still read one character at a time: iterator ranges that are not contiguous (e.g.
+`#!cpp std::list<char>` or `#!cpp std::istreambuf_iterator<char>`), wide strings, and user-defined adapters. An
+iterator pair over non-contiguous but random-access storage (e.g. `#!cpp std::deque<char>::iterator`) gets the first
+optimization but not the second, since the byte-scanning fast path requires contiguous storage.
+
+Practically: a file can be passed directly to `parse`, which also avoids the memory for a copy of the file. Reading it
+into a string first is no longer necessary for speed:

 ```cpp
-// gets the contiguous fast paths
+// fast: the stream buffer's get area is scanned in bulk
 std::ifstream f("example.json");
-std::string contents((std::istreambuf_iterator<char>(f)), std::istreambuf_iterator<char>());
-json j = json::parse(contents);
-
-// does not: input_stream_adapter has no fast path
-std::ifstream f2("example.json");
-json j2 = json::parse(f2);
+json j = json::parse(f);
 ```

+Two macros switch the stream optimizations off without changing any result:
+[`JSON_DISABLE_STREAM_BULK_SCAN`](../api/macros/json_disable_stream_bulk_scan.md) for stream buffers that do not follow
+the usual `#!cpp std::streambuf` contract, and
+[`JSON_DISABLE_UNLOCKED_FILE_IO`](../api/macros/json_disable_unlocked_file_io.md) for programs in which another thread
+must use the same `#!cpp FILE` object while it is parsed.
+
 For contiguous input with many non-ASCII characters, [`JSON_USE_SIMDUTF`](../api/macros/json_use_simdutf.md) can
 additionally speed up UTF-8 validation by using the [simdutf](https://github.com/simdutf/simdutf) library instead of
 the built-in scalar validator; streaming inputs (files, `#!cpp std::istream`, wide strings, user-defined adapters)
@@ -115,7 +122,9 @@ an adapter, since their template argument order does not match what `basic_json`
  [linear in its size](../api/basic_json/basic_json.md#complexity) for the copy constructor but
  [constant](../api/basic_json/basic_json.md#complexity) for the move constructor. The same applies to assigning a
  large `#!cpp std::string`, `#!cpp std::vector`, or other container into a value: pass it as `#!cpp std::move(x)`
-  rather than `x` whenever `x` is no longer needed afterwards.
+  rather than `x` whenever `x` is no longer needed afterwards. Since version 3.13.0, converting an rvalue container
+  (`#!cpp json j = std::move(vec);`) moves the elements instead of copying them; the source is then left in a valid but
+  unspecified state.
 - **Access without copying.** [`get<T>()`](../api/basic_json/get.md) returns a copy of the stored value converted to
  `T`. When a reference or pointer to the value already stored inside the `basic_json` is enough,
  [`get_ref()`](../api/basic_json/get_ref.md) and [`get_ptr()`](../api/basic_json/get_ptr.md) access it directly:
@@ -144,6 +153,29 @@ an adapter, since their template argument order does not match what `basic_json`
  ["reserving array capacity"](element_access/unchecked_access.md#performance-reserving-array-capacity) for the
  one-line recipe.

+## Memory
+
+- **A value is small, its content is on the heap.** A `basic_json` is 16 bytes on a 64-bit platform (a type tag and a
+  union). Strings, arrays, objects, and binary values are allocated on the heap and owned by the value. Destroying the
+  value frees everything it owns.
+- **Copies are deep.** After `#!cpp json b = a;`, changing `b` does not change `a`, and both own their memory. Copying a
+  large value therefore doubles its memory; see [Avoiding copies](#avoiding-copies). `#!cpp auto x = j["key"];` is a
+  copy, `#!cpp auto& x = j["key"];` is not.
+- **A moved-from value is `null`.** After `#!cpp json c = std::move(a);` the value `a` is `#!json null` and owns nothing.
+- **Reading does not require a tree.** If you only read the data, parse it into a [`json_document`](json_view.md)
+  (`#!cpp <nlohmann/json_view.hpp>`, added in version 3.13.0) instead of a `basic_json`. It stores 16 bytes per value, does not copy floating-point
+  numbers or strings without escape sequences out of the text, and creates no `basic_json` value except for the parts
+  you [`materialize()`](../api/basic_json_view/materialize.md). A document that borrows the text needs the text to
+  outlive it; see [Zero-copy JSON views](json_view.md).
+- **Containers keep their capacity.** `clear()` and `erase()` on an array remove the elements, but the underlying
+  `#!cpp std::vector` keeps its allocated capacity, like `#!cpp std::vector::clear` does. To give the memory back,
+  assign a new value (`#!cpp j = json::array();`) or destroy the value.
+- **Freed memory does not always go back to the operating system.** The library returns memory to the allocator
+  (`#!cpp std::allocator` by default, or the [one you configured](types/template_parameters.md)). Whether the process
+  size shrinks then depends on the allocator and the platform, as for any C++ program. A process that parses a large
+  document and drops it is not leaking if its resident size stays high; run it under a tool such as
+  [Valgrind](https://valgrind.org) or the sanitizers to tell a leak from retained memory.
+
 ## Serialization

 [`dump()`](../api/basic_json/dump.md) with the default `#!cpp indent = -1` selects "the most compact representation"
@@ -0,0 +1,122 @@
+# Recipes for Common Types
+
+The library converts the standard containers, strings, numbers, tuples, `std::optional`, and `std::filesystem::path`
+(the last two since version 3.12.0, C++17) out of the box, and your own types once you write conversion functions or use
+the macros (see [Arbitrary type conversions](arbitrary_types.md)). It deliberately does **not** convert smart pointers,
+`std::variant`, `std::chrono` types, or class hierarchies, because there is more than one reasonable JSON
+representation for each of them. This page shows a representation for each that you can copy and adapt.
+
+All recipes use a specialization of [`adl_serializer`](../api/adl_serializer/index.md), which you may provide for types
+you do not own, or free `to_json`/`from_json` functions in the namespace of the type. Place them where they are
+visible before any code that converts the type; see
+[Why isn't my `to_json` found?](arbitrary_types.md#why-isnt-my-to_json-or-from_json-found).
+
+## Smart pointers
+
+A `std::shared_ptr<T>` or `std::unique_ptr<T>` is written as the value it points to, or as `#!json null` for an empty
+pointer, and read back by allocating a new `T`:
+
+??? example "Example: serialize shared_ptr and unique_ptr"
+
+    ```cpp
+    --8<-- "examples/type_recipes_smart_pointers.c++14.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/type_recipes_smart_pointers.c++14.output"
+    ```
+
+With this, containers of smart pointers, pointers to `const`, and members of these types in your own structs convert as
+usual. A pointer to a base class cannot be filled this way, because `T` would have
+to be created as a derived type; see the next section.
+
+Reading creates a new object. Two `shared_ptr`s that pointed to the same object are written twice and read back as two
+separate objects.
+
+## Class hierarchies
+
+!!! tip "Derived classes whose type is known at compile time"
+
+    If you only need to serialize the data members of a derived class, and the code always knows the concrete type, you do
+    not need a type tag. The [`NLOHMANN_DEFINE_DERIVED_TYPE_*` macros](arbitrary_types.md#simplify-your-life-with-macros)
+    (since version 3.12.0) add the members of the derived class to those of its base class. This section is for the case
+    where the concrete type is only known at run time, such as a `std::unique_ptr<shape>` that holds a circle or a
+    rectangle.
+
+JSON has no notion of types, so a value in a hierarchy needs a **type tag** that says which derived class to create.
+Write the tag in the object, and select the class from it when reading:
+
+??? example "Example: serialize a class hierarchy with a type tag"
+
+    ```cpp
+    --8<-- "examples/type_recipes_class_hierarchy.c++14.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/type_recipes_class_hierarchy.c++14.output"
+    ```
+
+A `#!cpp std::vector<std::unique_ptr<shape>>` converts to an array of tagged objects and back, creating a `circle`
+and a `rectangle`. The same works for `std::shared_ptr<shape>`. Remember the virtual destructor: without it, deleting a
+derived object through the base pointer is undefined behavior.
+
+## `std::variant`
+
+A variant has the same problem: the alternative must be recorded. If the alternatives are your own types, write a type
+tag next to their members, exactly as for a hierarchy:
+
+??? example "Example: serialize a std::variant with a type tag"
+
+    ```cpp
+    --8<-- "examples/type_recipes_variant.c++17.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/type_recipes_variant.c++17.output"
+    ```
+
+In the example, the functions are found
+because `geo` is the namespace of the template arguments of `#!cpp std::variant<circ, rect>`; for a variant of only
+standard types (for example `#!cpp std::variant<int, std::string>`) there is no such namespace, and you need an
+`adl_serializer` specialization or a wrapper type of your own.
+
+If the alternatives are JSON-native (numbers, strings, ...), a variant such as `#!cpp std::variant<int, std::string>`
+can instead be written as the plain value, and read by testing the JSON type (`is_number_integer()`, `is_string()`)
+to choose the alternative.
+
+## `std::chrono`
+
+A duration is written as its count and read back with the same representation and period. The **unit is not part of
+the JSON value**, so document it, for example in the member name (`timeout_ms`):
+
+??? example "Example: serialize durations and system_clock time points"
+
+    ```cpp
+    --8<-- "examples/type_recipes_chrono.cpp"
+    ```
+
+    Output:
+
+    ```
+    --8<-- "examples/type_recipes_chrono.output"
+    ```
+
+A `system_clock::time_point` with millisecond precision is written as the number of milliseconds since the Unix epoch.
+The time point serializer is limited to `system_clock`,
+because the epoch of other clocks (for example `steady_clock`) has no meaning outside the running program.
+
+If you prefer a text representation such as ISO 8601 (`2023-11-14T22:13:20Z`), write the string with
+`#!cpp std::format("{:%FT%TZ}", t)` and read it with `std::chrono::parse` (both C++20), or with a date library, in the
+same two functions.
+
+## See also
+
+- [Arbitrary type conversions](arbitrary_types.md) - the conversion mechanism and macros
+- [Why isn't my `to_json` found?](arbitrary_types.md#why-isnt-my-to_json-or-from_json-found)
+- [Converting values](conversions.md) - `get`, implicit conversions, and `std::optional`
@@ -64,7 +64,7 @@ below are relative to `include/nlohmann`.
 |-----------|----------|
 | Value type enumeration | [`detail/value_t.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/value_t.hpp) |
 | Input adapters | [`detail/input/input_adapters.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/input_adapters.hpp) |
-| Lexer | [`detail/input/lexer.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/lexer.hpp), [`detail/input/number_parse.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/number_parse.hpp), [`detail/input/string_scan.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/string_scan.hpp) |
+| Lexer | [`detail/input/lexer.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/lexer.hpp), [`detail/input/number_parse.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/number_parse.hpp), [`detail/input/string_scan.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/string_scan.hpp), [`detail/input/simd_scan.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/simd_scan.hpp) |
 | Parser | [`detail/input/parser.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/parser.hpp) |
 | SAX interface and DOM builders | [`detail/input/json_sax.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/json_sax.hpp) |
 | Binary format readers | [`detail/input/binary_reader.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/binary_reader.hpp) |
@@ -339,6 +339,11 @@ The `serializer` (used by [`dump`](../api/basic_json/dump.md) and [`operator<<`]
 - `output_stream_adapter` writes to a `std::ostream`.
 - `output_string_adapter` appends to a string.

+The `binary_writer` does not call an adapter for every byte. The `to_*` functions that return a `std::vector` write
+into the vector through a sink (`output_vector_sink`) that is not virtual. The functions that take an output adapter
+write through a sink (`output_adapter_sink`) that collects the output in a buffer of one kibibyte and passes it to the
+adapter in blocks, so that the adapter is called (and a stream locked) once per block instead of once per value.
+
 ## Value conversion

 Values are converted from and to other types with the `JSONSerializer` template parameter. The default,
@@ -10,6 +10,29 @@ at its root, a [Natvis](https://learn.microsoft.com/en-us/visualstudio/debugger/
 file that gives `json`/`ordered_json` values a friendly, key/value debugger view instead of showing raw internal
 fields, when debugging with the MSVC debug engine (`cppvsdbg`) in Visual Studio or VS Code.

+The checked-in visualizers cover namespace variants with zero, one, or two ABI tags. Configurations with three or more
+ABI tags are not covered and may show raw internal fields instead. To generate a Natvis file for such a configuration:
+
+1. Check out the release tag of the library version you use.
+2. List the ABI tags and the macros that enable them:
+
+    ```shell
+    make natvis NATVIS_ARGS="--list-tags"
+    ```
+
+3. Generate a Natvis file with the tags of your configuration, for example for `JSON_DIAGNOSTICS`,
+    `JSON_DIAGNOSTIC_POSITIONS`, and `JSON_VIEW_NO_SIMD`:
+
+    ```shell
+    make natvis NATVIS_ARGS="--abi-tags _diag,_dp,_vns --output my_nlohmann_json.natvis"
+    ```
+
+4. Use the generated file instead of `nlohmann_json.natvis`.
+
+`--abi-tags` can be repeated for several configurations, and `--all` generates every combination (about 60 MB for 12
+ABI tags, doubling with each further tag). See
+[`tools/generate_natvis`](https://github.com/nlohmann/json/tree/develop/tools/generate_natvis) for all options.
+
 Debug engines that wrap LLDB instead of the MSVC debug engine (for example, `codelldb` in VS Code) only have
 partial/experimental Natvis support, and commonly fall back to showing raw internal fields even with the
 `.natvis` file present. Switching to `cppvsdbg` where available, or checking your debug extension's own Natvis
@@ -39,6 +39,8 @@ classDiagram

 Exceptions are used widely within the library. They can, however, be switched off with either using the compiler flag `-fno-exceptions` or by defining the symbol [`JSON_NOEXCEPTION`](../api/macros/json_noexception.md). In this case, exceptions are replaced by `abort()` calls. You can further control this behavior by defining `JSON_THROW_USER` (overriding `#!cpp throw`), `JSON_TRY_USER` (overriding `#!cpp try`), and `JSON_CATCH_USER` (overriding `#!cpp catch`).

+See [Working without exceptions](../features/no_exceptions.md) for the functions that report errors without throwing.
+
 Note that [`JSON_THROW_USER`](../api/macros/json_throw_user.md) should leave the current scope (e.g., by throwing or aborting), as continuing after it may yield undefined behavior.

 ??? example "Example: switch off exceptions and log errors before aborting"
@@ -192,6 +194,34 @@ This error indicates a syntax error while deserializing a JSON text. The error m
    - Make sure the input is correctly read. Try to write the input to standard output to check if, for instance, the input file was successfully opened.
    - Paste the input to a JSON validator like <https://jsonlint.com> or a tool like [jq](https://jqlang.github.io/jq/).

+??? info "Parsing a file fails at line 1, column 1 (or \"unexpected end of input\")"
+
+    The messages `attempting to parse an empty input` (since version 3.11.3) and `unexpected end of input` (also the message of
+    earlier versions for an empty input) at the very start of the input mean
+    that the parser did not see a single character. The library only reads from the stream it is given: it does not
+    open files and cannot tell a missing file from an empty one. The usual causes are:
+
+    - **The file was not opened.** A relative path is resolved against the *working directory of the running program*,
+      not against the source file or the project. IDEs and build tools often start the program in a build directory
+      (for example `build/` or `cmake-build-debug/`), so `"example.json"` may need to be `"../example.json"`. Use an
+      absolute path to rule this out.
+    - **The file is empty**, or a previous run truncated it (for example when it was opened for writing).
+    - **The stream was already read.** A stream whose content has been consumed (by printing it with
+      `std::cout << file.rdbuf()`, or by an earlier `accept`/`parse`/`>>`) is at its end. Parse it once, or rewind it
+      with `seekg(0)` after clearing the state with `clear()`.
+
+    Check the stream before parsing it:
+
+    ```cpp
+    std::ifstream f("example.json");
+    if (!f.is_open())
+    {
+        std::cerr << "cannot open example.json\n";
+        return 1;
+    }
+    json data = json::parse(f);
+    ```
+
 ### json.exception.parse_error.102

 JSON uses the `\uxxxx` format to describe Unicode characters. Code points above 0xFFFF are split into two `\uxxxx` entries ("surrogate pairs"). This error indicates that the surrogate pair is incomplete or contains an invalid code point.
@@ -58,6 +58,208 @@ json j{obj};   // -> {"key":"value"}  (copy, not array)

 Without the macro (default behavior), `json j{obj}` creates `[{"key":"value"}]`. This opt-in macro fixes issue #5074 while preserving backwards compatibility for existing code.

+## Getting started
+
+### Which file do I need?
+
+!!! question
+
+    Do I have to clone the repository or build the library?
+
+No. The library is header-only: the single file [`json.hpp`](https://github.com/nlohmann/json/releases) from the
+releases page is all you need, including the `_json` literals. Put it in a directory `nlohmann` on your include path.
+Companion headers (`json_fwd.hpp`, `json_view.hpp`, `json_literals.hpp`) are only needed if you use them. See
+[Integration](../integration/index.md#header-only).
+
+### Using CMake or a package manager
+
+!!! question
+
+    How do I add the library with CMake, Conan, vcpkg, Homebrew, or another tool?
+
+See [CMake](../integration/cmake.md) for `find_package`, `add_subdirectory`, and `FetchContent`, and
+[Package managers](../integration/package_managers.md) for the list of supported package managers.
+
+### The IDE cannot open the header
+
+!!! question
+
+    The compiler finds `nlohmann/json.hpp`, but my IDE reports "cannot open source file". Why?
+
+The compiler's include path is set correctly, but the IDE's is not. Add the same directory to the include paths of the
+IDE (or of its language server); the build itself is not affected.
+
+### Compile times
+
+!!! question
+
+    Including the library slows down my build. What can I do?
+
+Include [`json_fwd.hpp`](../integration/compile_times.md#include-json_fwdhpp-in-headers) in headers and `json.hpp` only
+in the source files that need it, instantiate `basic_json` once, and consider precompiled headers or
+[C++20 modules](../features/modules.md). See [Compile times](../integration/compile_times.md).
+
+## Parsing
+
+### Parsing a file fails with "unexpected end of input"
+
+!!! question
+
+    `json::parse(file)` throws `parse_error.101` at line 1, column 1 for a file that is valid JSON. Why?
+
+The parser did not see any character: the file was most likely not opened. A relative path is resolved against the
+working directory of the running program, which is often the build directory of your IDE, not the source directory.
+Check `is_open()` and try an absolute path. Other causes are an empty file and a stream that was already read. See
+[`parse_error.101`](exceptions.md#jsonexceptionparse_error101).
+
+### Input that arrives in chunks
+
+!!! question
+
+    My data comes from a socket in pieces. How do I parse it?
+
+The parser cannot be resumed. Frame the messages (one value per line, a length prefix) and parse each complete frame, or
+buffer the chunks until the value is complete; a `parse_error` at the end of the buffer means the input ended
+prematurely. See [Large, streamed, and partial input](../features/parsing/large_and_partial_input.md#input-arriving-in-chunks).
+
+### Several values in one stream
+
+!!! question
+
+    How do I read concatenated JSON values or one value per line?
+
+Read newline-delimited input line by line ([JSON Lines](../features/parsing/json_lines.md)). For concatenated values, use
+`operator>>` and check for the end of the stream before each read, as shown in
+[Several values in one stream](../features/parsing/large_and_partial_input.md#several-values-in-one-stream).
+
+### Files that are too large for memory
+
+!!! question
+
+    How do I process a huge JSON file?
+
+Handle and discard the records of a large array with a [parser callback](../features/parsing/parser_callbacks.md), stop
+early with the [SAX interface](../features/parsing/sax_interface.md), or read parts of the text through a
+[`json_document`](../features/json_view.md) (added in version 3.13.0). See
+[Input too large for memory](../features/parsing/large_and_partial_input.md#input-too-large-for-memory).
+
+### Position of a parse error
+
+!!! question
+
+    How do I get the line and column of a parse error?
+
+The message contains them. The exception stores the byte index in `byte`, from which you can compute both; see
+[Where did the error occur?](../features/parsing/parse_exceptions.md#where-did-the-error-occur). To locate a value that
+causes a *later* error, such as a `type_error`, use
+[`JSON_DIAGNOSTIC_POSITIONS`](../features/parsing/parse_exceptions.md#where-is-the-value-that-caused-a-later-error).
+
+### Comments and trailing commas
+
+!!! question
+
+    Can the parser read JSON with comments or trailing commas?
+
+Yes, when asked to: see [Comments](../features/comments.md) and [Trailing commas](../features/trailing_commas.md). Both
+are rejected by default.
+
+## Accessing and creating values
+
+### Reading a value into a variable
+
+!!! question
+
+    How do I get a C++ value out of a `json` value?
+
+Use [`get<T>()`](../api/basic_json/get.md), for example `#!cpp int age = j["age"].get<int>();`, or an implicit conversion.
+`#!cpp auto x = j["age"];` is **not** a conversion: it copies the `json` value. See
+[Converting values](../features/conversions.md).
+
+### Strings are printed with quotes
+
+!!! question
+
+    `std::cout << j["name"]` prints `"Mary"` with quotes. How do I get the string?
+
+The value is a `json`, and printing it produces JSON text. Convert it first: `#!cpp j["name"].get<std::string>()`. See
+[Getting a string without quotes](../features/conversions.md#getting-values-out).
+
+### Testing whether a key exists
+
+!!! question
+
+    How do I check if a key exists, without changing the object?
+
+Use `contains` or `find`. Do not test with the non-const `operator[]`: like `std::map::operator[]`, it inserts a `null`
+value for a missing key. See [Does this key exist?](../features/element_access/index.md#does-this-key-exist).
+
+### Reading a value with a fallback
+
+!!! question
+
+    How do I read a value that may be missing?
+
+Use [`value`](../features/element_access/default_value.md), which returns a default for a missing key. It still throws if
+the key exists with a different type; see [Working without exceptions](../features/no_exceptions.md).
+
+### Iterating and nested values
+
+!!! question
+
+    How do I loop over an array or object, or reach a nested value?
+
+See [Iterators](../features/iterators.md) and [`items()`](../api/basic_json/items.md) for loops, and
+[JSON Pointer](../features/json_pointer.md) to address or test a nested value by path.
+
+### Unexpected arrays when creating values
+
+!!! question
+
+    Why does `json j{x}` or `{{"a", 1}, {"b"}}` produce an array instead of what I expected?
+
+Braces create arrays and objects based on their content, and single-element braces create a one-element array. See
+[Brace initialization yields arrays](#brace-initialization-yields-arrays) and the table in
+[Creating values](../features/creating_values.md#what-does-this-produce).
+
+### Keeping the order of object keys
+
+!!! question
+
+    The keys of my object come out sorted. How do I keep the insertion order?
+
+Use `ordered_json`, and call `ordered_json::parse` when reading. See [Object order](../features/object_order.md).
+
+## Converting your own types
+
+### Structs, enums, and optional fields
+
+!!! question
+
+    How do I convert my own types to and from JSON?
+
+Write `to_json`/`from_json` functions or use the `NLOHMANN_DEFINE_TYPE_*` macros; see
+[Arbitrary type conversions](../features/arbitrary_types.md). Enums can be mapped to strings
+([Enum conversion](../features/enum_conversion.md)), and an empty `std::optional` can be omitted
+([Omitting a field](../features/conversions.md#omitting-a-field-when-serializing-stdoptional)).
+
+### Smart pointers, variants, chrono, and class hierarchies
+
+!!! question
+
+    Why can't I convert `std::shared_ptr`, `std::variant`, `std::chrono` types, or a pointer to a base class?
+
+There is more than one sensible JSON representation for them, so the library leaves the choice to you.
+[Recipes for common types](../features/type_recipes.md) shows one for each.
+
+### My `to_json` is not found
+
+!!! question
+
+    I wrote `to_json`/`from_json`, but the compiler does not find them. Why?
+
+Typical causes are a type alias of a standard type, a function in the wrong namespace, or a declaration that comes too
+late. See [Why isn't my `to_json` found?](../features/arbitrary_types.md#why-isnt-my-to_json-or-from_json-found).
+
 ## Limitations

 ### Relaxed parsing
@@ -202,6 +404,36 @@ Not directly, but the companion project [json-schema-validator](https://github.c
 builds JSON Schema (draft 7; draft 4 in its older, now-superseded 1.x releases) validation on top of this library
 and is a common recommendation for this use case.

+### Memory use
+
+!!! question
+
+    Does the library leak memory? My process stays large after I free a `json` value.
+
+Destroying a value frees everything it owns. Freed memory is returned to the allocator, which does not necessarily give
+it back to the operating system, so a high resident size alone is not a leak. Copies are deep, and `clear()` keeps the
+capacity of an array. See [Memory](../features/performance.md#memory), and use Valgrind or the sanitizers to tell a leak
+from retained memory.
+
+### Reproducible builds
+
+!!! question
+
+    The header path ends up in my binary. How do I get path-independent builds?
+
+The runtime assertions embed `__FILE__`. Define `NDEBUG` (the default for release builds) or map the path prefix; see
+[Notes for builds and distribution](../integration/index.md#notes-for-builds-and-distribution).
+
+### Slow debug builds
+
+!!! question
+
+    Parsing a large file is very slow in my debug build. Can I compile the library with optimizations?
+
+The library is header-only, so there is no separate source file. Keep the code that uses `json` in its own source file and
+compile that file with optimizations; see
+[Notes for builds and distribution](../integration/index.md#notes-for-builds-and-distribution).
+
 ## Exceptions

 ### Parsing without exceptions
@@ -210,7 +442,8 @@ and is a common recommendation for this use case.

    Is it possible to indicate a parse error without throwing an exception?

-Yes, see [Parsing and exceptions](../features/parsing/parse_exceptions.md).
+Yes, see [Parsing and exceptions](../features/parsing/parse_exceptions.md) and
+[Working without exceptions](../features/no_exceptions.md).


 ### Key name in exceptions
@@ -29,6 +29,10 @@ int main()
    j["name"] = "Niels";
    j["list"] = {1, 0, 2};

+    // read a value into a C++ variable and use it
+    double pi = j["pi"].get<double>();
+    std::cout << "2 * pi = " << 2 * pi << '\n';
+
    // serialize with an indent of 4 spaces
    std::cout << j.dump(4) << '\n';
 }
@@ -43,6 +43,21 @@ using json = nlohmann::json;
 to the files you want to process JSON and set the necessary switches to enable C++11 (e.g., `-std=c++11` for GCC and
 Clang).

+!!! tip "Which file do I download?"
+
+    For a project without a package manager, the library itself, including the `_json` literals, is **one file**:
+    [`json.hpp`](https://github.com/nlohmann/json/releases/latest/download/json.hpp) from the
+    [releases page](https://github.com/nlohmann/json/releases). You do not need to clone the repository, build
+    anything, or link a library. Put the file in a directory named `nlohmann` that is on your include path (for
+    example `third_party/nlohmann/json.hpp` with `-I third_party`), so that `#include <nlohmann/json.hpp>` works.
+    Download the companion headers listed below only if you use them: `json_view.hpp` for the
+    [zero-copy views](../features/json_view.md), `json_fwd.hpp` for forward declarations, and `json_literals.hpp` if
+    you define `JSON_NO_AUTOMATIC_UDLS`. Keep them in the same `nlohmann` directory.
+
+    Do not copy only parts of the repository's `include/` directory: the headers in it include each other and must be
+    kept together. If your IDE reports "cannot open source file" while the compiler succeeds, the compiler's include
+    path is set correctly but the IDE's is not; add the same directory to the IDE's include paths.
+
 You can further use file
 [`single_include/nlohmann/json_fwd.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json_fwd.hpp)
 for forward declarations (see [Compile times](compile_times.md)), and file
@@ -54,3 +69,21 @@ For the read-only, non-owning [`basic_json_document`](../api/basic_json_document
 types, additionally include
 [`single_include/nlohmann/json_view.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json_view.hpp);
 see [Zero-copy JSON views](../features/json_view.md).
+
+## Notes for builds and distribution
+
+**Reproducible and path-independent builds.** The runtime assertions use `assert`, which embeds the name of the source
+file (`__FILE__`) in the binary. Release builds do not contain them, because they define `NDEBUG`. If you compile with
+assertions enabled and need binaries that do not depend on the build directory, either define `NDEBUG` or map the
+prefix of the path with the compiler option `-ffile-prefix-map=<old>=<new>` (GCC 8 and later, Clang 10 and later). See
+[Runtime assertions](../features/assertions.md).
+
+**There is no separate source file to compile.** The library is header-only, so there is no `.cpp` that could be
+built with different options than the code that includes it. It is also not available as a precompiled library. To
+compile the library with optimizations in an otherwise unoptimized build (for example to parse large files in a debug
+build, which is slow because of the unoptimized code and the checks of the debug standard library), keep the code that
+uses `json` in a separate source file and set the options for that file only. [Compile times](compile_times.md)
+shows how to [instantiate `basic_json` once](compile_times.md#instantiate-basic_json-once).
+
+**Debugger visualization.** The Natvis file works with the Visual Studio debugger, including the `cppvsdbg` engine in
+Visual Studio Code, but not with debuggers that wrap LLDB, such as `codelldb`; see [Debugging](../home/debugging.md).
@@ -60,6 +60,7 @@ nav:
  - Features:
      - features/index.md
      - features/arbitrary_types.md
+      - features/type_recipes.md
      - Binary Formats:
          - features/binary_formats/index.md
          - features/binary_formats/bjdata.md
@@ -84,11 +85,13 @@ nav:
      - features/modifying_values.md
      - features/modules.md
      - 'nlohmann Namespace': features/namespace.md
+      - features/no_exceptions.md
      - features/object_order.md
      - features/performance.md
      - Parsing:
          - features/parsing/index.md
          - features/parsing/json_lines.md
+          - features/parsing/large_and_partial_input.md
          - features/parsing/parse_exceptions.md
          - features/parsing/parser_callbacks.md
          - features/parsing/sax_interface.md
@@ -383,6 +386,7 @@ nav:
          - 'JSON_NO_AUTOMATIC_UDLS': api/macros/json_no_automatic_udls.md
          - 'JSON_NOEXCEPTION': api/macros/json_noexception.md
          - 'JSON_NO_IO': api/macros/json_no_io.md
+          - 'JSON_NO_SIMD': api/macros/json_no_simd.md
          - 'JSON_NO_THREAD_LOCAL': api/macros/json_no_thread_local.md
          - 'JSON_PRECISE_STREAM_POSITION': api/macros/json_precise_stream_position.md
          - 'JSON_SKIP_LIBRARY_VERSION_CHECK': api/macros/json_skip_library_version_check.md
@@ -6,7 +6,7 @@
    "": {
      "name": "check-mermaid",
      "dependencies": {
-        "jsdom": "30.1.2",
+        "jsdom": "30.1.3",
        "mermaid": "11.17.2"
      }
    },
@@ -40,9 +40,9 @@
      }
    },
    "node_modules/@asamuzakjp/dom-selector": {
-      "version": "9.2.4",
-      "resolved": "https://registry.npmjs.org/@asamuzakjp/dom-selector/-/dom-selector-9.2.4.tgz",
-      "integrity": "sha512-YnVzxDxLaqL0t7Q4wfcgHZjg55Wm6y5EaO7Bhu3q9J7wq/8iw3PhsnWiOQhYekx4VexnbkgWpTT6n+QIV7kczw==",
+      "version": "10.0.3",
+      "resolved": "https://registry.npmjs.org/@asamuzakjp/dom-selector/-/dom-selector-10.0.3.tgz",
+      "integrity": "sha512-3+777rEPsOOjoy5/sRmIzHnoRDaLpm3XWY2dmWn/N7f/XwDG0bcpnFaKL3X9FYJUbNwLmpcJC1bUYexJRxsFlw==",
      "license": "MIT",
      "dependencies": {
        "bidi-js": "^1.1.0",
@@ -1105,9 +1105,9 @@
      }
    },
    "node_modules/dompurify": {
-      "version": "3.4.16",
-      "resolved": "https://registry.npmjs.org/dompurify/-/dompurify-3.4.16.tgz",
-      "integrity": "sha512-sqo+pNp3qRhCIpbgRi1y8Tgk27Bo2Ry7w0dC1NBeNTdZChWjz9Xb/KOoZbRP/R6pQZ80Qw8YhXw13hWWBbMRnQ==",
+      "version": "3.4.17",
+      "resolved": "https://registry.npmjs.org/dompurify/-/dompurify-3.4.17.tgz",
+      "integrity": "sha512-B/pSlYVHQ58kqISD/yDjuJ1yfzI34m1gF4lAod2bwSRhiN4K5Cl3H8Af7hqB2PmTL911tdEudnnXn5FnhRoz0w==",
      "license": "(MPL-2.0 OR Apache-2.0)",
      "optionalDependencies": {
        "@types/trusted-types": "^2.0.7"
@@ -1202,13 +1202,13 @@
      "license": "MIT"
    },
    "node_modules/jsdom": {
-      "version": "30.1.2",
-      "resolved": "https://registry.npmjs.org/jsdom/-/jsdom-30.1.2.tgz",
-      "integrity": "sha512-0FFE/jE1rppmVfUrJUgxqXjcwolZYIGtAgj1pTussMhNZxIxi7W/PvfWaMNroGi2B36X1IKHbexpZ9DhkoOPiQ==",
+      "version": "30.1.3",
+      "resolved": "https://registry.npmjs.org/jsdom/-/jsdom-30.1.3.tgz",
+      "integrity": "sha512-hQMUPvRgN7KxsfIytDQji7bimuJeRQa6Qo5+iuiZQk5CafeRxLIA10/cG5YCBFNpD9RO3oqIiN4CO1Y44kxqXg==",
      "license": "MIT",
      "dependencies": {
        "@asamuzakjp/css-color": "^7.1.3",
-        "@asamuzakjp/dom-selector": "^9.2.4",
+        "@asamuzakjp/dom-selector": "^10.0.3",
        "@bramus/specificity": "^2.4.2",
        "@csstools/css-syntax-patches-for-csstree": "^1.1.15",
        "@exodus/bytes": "^1.16.0",
@@ -1221,7 +1221,7 @@
        "parse5": "^8.0.1",
        "saxes": "^6.0.0",
        "tough-cookie": "^6.0.2",
-        "undici": "^8.11.2",
+        "undici": "^8.12.1",
        "w3c-xmlserializer": "^6.0.0",
        "webidl-conversions": "^8.0.1",
        "whatwg-mimetype": "^5.0.0",
@@ -1521,9 +1521,9 @@
      }
    },
    "node_modules/undici": {
-      "version": "8.11.2",
-      "resolved": "https://registry.npmjs.org/undici/-/undici-8.11.2.tgz",
-      "integrity": "sha512-u4UB2/IrKdU6lFxumHmmo1a3fCQO5tzQllRorfoRS63txhrB7xTpSn1PftwC4qEHkOaqP95fCWW4lJzwErwzhQ==",
+      "version": "8.12.2",
+      "resolved": "https://registry.npmjs.org/undici/-/undici-8.12.2.tgz",
+      "integrity": "sha512-XtuDWVdqTLr3NAxm2ly9/hU6kUsJOgGh1RASzMBbsw6aWCOaQzHdW+QQDfdERjfJ2V5vL5pRPa4RetO9UfivDg==",
      "license": "MIT",
      "engines": {
        "node": ">=22.19.0"
@@ -4,7 +4,7 @@
  "description": "Validate the Mermaid diagrams of the documentation (see check_mermaid.mjs)",
  "type": "module",
  "dependencies": {
-    "jsdom": "30.1.2",
+    "jsdom": "30.1.3",
    "mermaid": "11.17.2"
  }
 }
@@ -122,6 +122,12 @@
    #define NLOHMANN_JSON_ABI_TAG_DISABLE_UNLOCKED_FILE_IO
 #endif

+#ifdef JSON_NO_SIMD
+    #define NLOHMANN_JSON_ABI_TAG_NO_SIMD _ns
+#else
+    #define NLOHMANN_JSON_ABI_TAG_NO_SIMD
+#endif
+
 #ifdef JSON_VIEW_NO_SIMD
    #define NLOHMANN_JSON_ABI_TAG_VIEW_NO_SIMD _vns
 #else
@@ -139,9 +145,9 @@
 #endif

 // Construct the namespace ABI tags component
-#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e, f, g, h, i, j, k, l) json_abi ## a ## b ## c ## d ## e ## f ## g ## h ## i ## j ## k ## l
-#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c, d, e, f, g, h, i, j, k, l) \
-    NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e, f, g, h, i, j, k, l)
+#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e, f, g, h, i, j, k, l, m) json_abi ## a ## b ## c ## d ## e ## f ## g ## h ## i ## j ## k ## l ## m
+#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c, d, e, f, g, h, i, j, k, l, m) \
+    NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c, d, e, f, g, h, i, j, k, l, m)

 #define NLOHMANN_JSON_ABI_TAGS                                       \
    NLOHMANN_JSON_ABI_TAGS_CONCAT(                                   \
@@ -155,6 +161,7 @@
            NLOHMANN_JSON_ABI_TAG_OBJECTS_FOR_ENUM_KEYED_MAPS,       \
            NLOHMANN_JSON_ABI_TAG_DISABLE_STREAM_BULK_SCAN,          \
            NLOHMANN_JSON_ABI_TAG_DISABLE_UNLOCKED_FILE_IO,          \
+            NLOHMANN_JSON_ABI_TAG_NO_SIMD,                           \
            NLOHMANN_JSON_ABI_TAG_VIEW_NO_SIMD,                      \
            NLOHMANN_JSON_ABI_TAG_VIEW_USE_SSSE3)

@@ -14,11 +14,24 @@
    #include <intrin0.h> // __umulh, _umul128, _BitScanForward64, _BitScanReverse64
 #endif

+#ifdef _MSC_VER
+    #include <cstdlib> // _byteswap_ushort, _byteswap_ulong, _byteswap_uint64
+#endif
+#if defined(_MSC_VER) && !defined(__clang__) && (defined(_M_IX86) || defined(_M_ARM))
+    #include <intrin.h> // _BitScanForward, _BitScanReverse
+#endif
+
 #include <nlohmann/detail/macro_scope.hpp> // JSON_HEDLEY_ALWAYS_INLINE, NLOHMANN_JSON_NAMESPACE_BEGIN

+#if defined(__cpp_lib_bit_cast) || defined(__cpp_lib_bitops) || defined(__cpp_lib_byteswap)
+    #include <bit> // bit_cast, byteswap, countl_zero, countr_zero
+#endif
+
 // Portable bit-level helpers for the number and string scanners. They use
-// compiler builtins or platform-specific intrinsics where available and plain
-// C++ otherwise, so they work regardless of byte order.
+// compiler builtins or platform-specific intrinsics where available, the
+// C++20 <bit> functions next, and plain C++ otherwise, so they work regardless
+// of byte order. (The builtins and intrinsics come first: MSVC's
+// std::countl_zero checks for LZCNT at run time unless AVX2 is enabled.)

 NLOHMANN_JSON_NAMESPACE_BEGIN
 namespace detail
@@ -33,6 +46,16 @@ inline int count_leading_zeros(std::uint64_t x) noexcept
    unsigned long index = 0; // NOLINT(runtime/int): the type _BitScan*64 takes
    _BitScanReverse64(&index, x);
    return 63 - static_cast<int>(index);
+#elif defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_ARM))
+    unsigned long index = 0; // NOLINT(runtime/int): the type _BitScan* takes
+    if (_BitScanReverse(&index, static_cast<unsigned long>(x >> 32u))) // NOLINT(runtime/int)
+    {
+        return 31 - static_cast<int>(index);
+    }
+    _BitScanReverse(&index, static_cast<unsigned long>(x)); // NOLINT(runtime/int)
+    return 63 - static_cast<int>(index);
+#elif defined(__cpp_lib_bitops)
+    return std::countl_zero(x);
 #else
    int n = 0;
    for (int shift = 32; shift != 0; shift >>= 1)
@@ -56,6 +79,16 @@ inline int count_trailing_zeros(std::uint64_t x) noexcept
    unsigned long index = 0; // NOLINT(runtime/int): the type _BitScan*64 takes
    _BitScanForward64(&index, x);
    return static_cast<int>(index);
+#elif defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_ARM))
+    unsigned long index = 0; // NOLINT(runtime/int): the type _BitScan* takes
+    if (_BitScanForward(&index, static_cast<unsigned long>(x))) // NOLINT(runtime/int)
+    {
+        return static_cast<int>(index);
+    }
+    _BitScanForward(&index, static_cast<unsigned long>(x >> 32u)); // NOLINT(runtime/int)
+    return 32 + static_cast<int>(index);
+#elif defined(__cpp_lib_bitops)
+    return std::countr_zero(x);
 #else
    int n = 0;
    for (int shift = 32; shift != 0; shift >>= 1)
@@ -70,6 +103,67 @@ inline int count_trailing_zeros(std::uint64_t x) noexcept
 #endif
 }

+/// the object representation of @a from as a @a To (std::bit_cast in C++20)
+template<typename To, typename From>
+JSON_HEDLEY_ALWAYS_INLINE To bit_cast(const From& from) noexcept
+{
+    static_assert(sizeof(To) == sizeof(From), "bit_cast needs types of the same size");
+#if defined(__cpp_lib_bit_cast)
+    return std::bit_cast<To>(from);
+#else
+    To to {};
+    std::memcpy(&to, &from, sizeof(To));
+    return to;
+#endif
+}
+
+/// x with its bytes in reverse order (std::byteswap in C++23); compilers lower
+/// it to a single bswap/rev/movbe
+inline std::uint16_t byteswap(std::uint16_t x) noexcept
+{
+#if defined(__GNUC__) || defined(__clang__)
+    return __builtin_bswap16(x);
+#elif defined(_MSC_VER)
+    return _byteswap_ushort(x);
+#elif defined(__cpp_lib_byteswap)
+    return std::byteswap(x);
+#else
+    return static_cast<std::uint16_t>((x >> 8u) | (x << 8u));
+#endif
+}
+
+/// x with its bytes in reverse order (std::byteswap in C++23)
+inline std::uint32_t byteswap(std::uint32_t x) noexcept
+{
+#if defined(__GNUC__) || defined(__clang__)
+    return __builtin_bswap32(x);
+#elif defined(_MSC_VER)
+    return _byteswap_ulong(x);
+#elif defined(__cpp_lib_byteswap)
+    return std::byteswap(x);
+#else
+    return ((x & 0x000000FFu) << 24u) | ((x & 0x0000FF00u) << 8u)
+           | ((x & 0x00FF0000u) >> 8u) | ((x & 0xFF000000u) >> 24u);
+#endif
+}
+
+/// x with its bytes in reverse order (std::byteswap in C++23)
+inline std::uint64_t byteswap(std::uint64_t x) noexcept
+{
+#if defined(__GNUC__) || defined(__clang__)
+    return __builtin_bswap64(x);
+#elif defined(_MSC_VER)
+    return _byteswap_uint64(x);
+#elif defined(__cpp_lib_byteswap)
+    return std::byteswap(x);
+#else
+    x = ((x & 0x00000000FFFFFFFFull) << 32u) | ((x & 0xFFFFFFFF00000000ull) >> 32u);
+    x = ((x & 0x0000FFFF0000FFFFull) << 16u) | ((x & 0xFFFF0000FFFF0000ull) >> 16u);
+    x = ((x & 0x00FF00FF00FF00FFull) << 8u) | ((x & 0xFF00FF00FF00FF00ull) >> 8u);
+    return x;
+#endif
+}
+
 /// the 128-bit product of two 64-bit numbers
 struct uint128_parts
 {
@@ -107,8 +201,8 @@ inline uint128_parts full_multiplication(std::uint64_t a, std::uint64_t b) noexc
 /// targets; always inlined, as GCC otherwise calls it in the number loops)
 JSON_HEDLEY_ALWAYS_INLINE std::uint64_t read_eight_bytes(const unsigned char* b) noexcept
 {
-#if defined(_MSC_VER) || defined(__x86_64__) || defined(__i386__) || (defined(__BYTE_ORDER__) && defined(__ORDER_LITTLE_ENDIAN__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__)
-    // the byte order already matches (all MSVC targets are little-endian)
+#if JSON_LITTLE_ENDIAN_TARGET
+    // the byte order already matches
    std::uint64_t result = 0;
    std::memcpy(&result, b, sizeof(result));
    return result;
@@ -18,17 +18,14 @@
 #include <limits> // numeric_limits
 #include <type_traits> // conditional

-#ifdef _MSC_VER
-    #include <cstdlib> // _byteswap_uint64
-#endif

 // SSE2 (every x86-64 CPU) and NEON (every 64-bit Arm CPU) convert the 16
-// digits of a double at once
-#if defined(__x86_64__) || (defined(_M_X64) && !defined(_M_ARM64EC))
+// digits of a double at once (unless JSON_NO_SIMD selects the portable code)
+#if !defined(JSON_NO_SIMD) && (defined(__x86_64__) || (defined(_M_X64) && !defined(_M_ARM64EC)))
    #include <emmintrin.h>
    #define JSON_DTOA_SSE2 1
    #define JSON_DTOA_NEON 0
-#elif (defined(__aarch64__) || defined(_M_ARM64)) && !defined(_M_ARM64EC) && !defined(__ARM_BIG_ENDIAN)
+#elif !defined(JSON_NO_SIMD) && (defined(__aarch64__) || defined(_M_ARM64)) && !defined(_M_ARM64EC) && !defined(__ARM_BIG_ENDIAN)
    #include <arm_neon.h>
    #define JSON_DTOA_SSE2 0
    #define JSON_DTOA_NEON 1
@@ -37,6 +34,7 @@
    #define JSON_DTOA_NEON 0
 #endif

+#include <nlohmann/detail/bit_ops.hpp>
 #include <nlohmann/detail/conversions/zmij.hpp>
 #include <nlohmann/detail/macro_scope.hpp>

@@ -66,16 +64,6 @@ For a detailed description of the algorithm see:
 namespace dtoa_impl
 {

-template<typename Target, typename Source>
-Target reinterpret_bits(const Source source)
-{
-    static_assert(sizeof(Target) == sizeof(Source), "size mismatch");
-
-    Target target;
-    std::memcpy(&target, &source, sizeof(Source));
-    return target;
-}
-
 struct diyfp // f * 2^e
 {
    static constexpr int kPrecision = 64; // = q
@@ -230,7 +218,7 @@ boundaries compute_boundaries(FloatType value)

    using bits_type = typename std::conditional<kPrecision == 24, std::uint32_t, std::uint64_t >::type;

-    const auto bits = static_cast<std::uint64_t>(reinterpret_bits<bits_type>(value));
+    const auto bits = static_cast<std::uint64_t>(bit_cast<bits_type>(value));
    const std::uint64_t E = bits >> (kPrecision - 1);
    const std::uint64_t F = bits & (kHiddenBit - 1);

@@ -1084,13 +1072,10 @@ inline std::uint64_t eight_digit_bytes(std::uint64_t abcdefgh) noexcept
 /// the byte stores once this is inlined)
 inline void store_msb_first(char* p, std::uint64_t v) noexcept
 {
-#if defined(__BYTE_ORDER__) && defined(__ORDER_LITTLE_ENDIAN__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
-    v = __builtin_bswap64(v);
+#if JSON_LITTLE_ENDIAN_TARGET
+    v = byteswap(v);
    std::memcpy(p, &v, sizeof(v));
-#elif defined(__BYTE_ORDER__) && defined(__ORDER_BIG_ENDIAN__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
-    std::memcpy(p, &v, sizeof(v));
-#elif defined(_MSC_VER) // (little-endian on all its targets)
-    v = _byteswap_uint64(v);
+#elif JSON_BIG_ENDIAN_TARGET
    std::memcpy(p, &v, sizeof(v));
 #else
    for (unsigned i = 0; i < 8; ++i)
@@ -1462,8 +1447,7 @@ char* write_positive_zmij(char* first, const char* last, FloatType value)
 {
    static_assert(is_binary64<FloatType>::value,
                  "internal error: the conversion of Zmij needs IEEE 754 binary64 numbers");
-    std::uint64_t bits = 0;
-    std::memcpy(&bits, &value, sizeof(bits));
+    const auto bits = bit_cast<std::uint64_t>(value);
    const zmij::shortest_decimal d = zmij::to_shortest(bits);
    if (JSON_HEDLEY_LIKELY(last - first >= 41))
    {
@@ -86,7 +86,7 @@ JSON_INLINE_VARIABLE constexpr std::size_t max_valueless_container_size = 1 << 2
 /*!
@brief deserialization of BJData, BON8, BSON, CBOR, MessagePack, and UBJSON values
 */
-template<typename BasicJsonType, typename InputAdapterType, typename SAX = json_sax_dom_parser<BasicJsonType, InputAdapterType>>
+template<typename BasicJsonType, typename InputAdapterType, typename SAX = json_sax_dom_binary_parser<BasicJsonType, InputAdapterType>>
 class binary_reader
 {
    using number_integer_t = typename BasicJsonType::number_integer_t;
@@ -8,17 +8,18 @@

 #pragma once

-#include <algorithm> // count, find, min
+#include <algorithm> // count, find, max, min
 #include <array> // array
 #include <cstddef> // size_t
 #include <cstdint> // uint32_t
 #include <cstring> // strlen
 #include <iterator> // begin, end, iterator_traits, random_access_iterator_tag, distance, next, reverse_iterator
 #include <limits> // numeric_limits
+#include <memory> // unique_ptr
 #include <streambuf> // streambuf
 #include <string> // string, char_traits
 #include <type_traits> // enable_if, is_base_of, is_pointer, is_integral, remove_pointer
-#include <utility> // pair, declval
+#include <utility> // declval, move, pair
 #include <vector> // vector

 #ifndef JSON_NO_IO
@@ -72,6 +73,82 @@ enum class input_format_t { json, cbor, msgpack, ubjson, bson, bjdata, bon8 };

 #ifndef JSON_NO_IO
 /*!
+A growable array of characters for the part of a token that an input adapter
+copied out of its window: unlike std::vector<char>::push_back(), appending a
+character takes no reference to a local, and is a few instructions when there
+is room.
+*/
+class token_carry_buffer
+{
+  public:
+    token_carry_buffer() = default;
+    token_carry_buffer(const token_carry_buffer&) = delete;
+    token_carry_buffer& operator=(const token_carry_buffer&) = delete;
+    token_carry_buffer(token_carry_buffer&& rhs) noexcept
+        : m_data(std::move(rhs.m_data)), m_end(rhs.m_end), m_capacity_end(rhs.m_capacity_end)
+    {
+        rhs.m_end = rhs.m_capacity_end = nullptr;
+    }
+    token_carry_buffer& operator=(token_carry_buffer&&) = delete;
+    ~token_carry_buffer() = default;
+
+    void clear() noexcept
+    {
+        m_end = m_data.get();
+    }
+
+    void push_back(char c)
+    {
+        if (JSON_HEDLEY_UNLIKELY(m_end == m_capacity_end))
+        {
+            grow(1);
+        }
+        *m_end++ = c;
+    }
+
+    void append(const char* first, const char* last)
+    {
+        const auto n = static_cast<std::size_t>(last - first);
+        const auto room = static_cast<std::size_t>(m_capacity_end - m_end);
+        if (n > room)
+        {
+            grow(n);
+        }
+        if (n != 0)
+        {
+            std::memcpy(m_end, first, n);
+        }
+        m_end += n;
+    }
+
+    /// replace the contents of @a out
+    void copy_to(std::vector<char>& out) const
+    {
+        out.assign(m_data.get(), m_end);
+    }
+
+  private:
+    /// make room for @a extra more characters
+    JSON_HEDLEY_NEVER_INLINE void grow(std::size_t extra)
+    {
+        const auto size = static_cast<std::size_t>(m_end - m_data.get());
+        const auto capacity = static_cast<std::size_t>(m_capacity_end - m_data.get());
+        const std::size_t new_capacity = (std::max)(capacity < 32 ? static_cast<std::size_t>(32) : 2 * capacity, size + extra);
+        std::unique_ptr<char[]> data(new char[new_capacity]); // NOLINT(cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays)
+        if (size != 0)
+        {
+            std::memcpy(data.get(), m_data.get(), size);
+        }
+        m_data = std::move(data);
+        m_end = m_data.get() + size;
+        m_capacity_end = m_data.get() + new_capacity;
+    }
+
+    std::unique_ptr<char[]> m_data{}; // NOLINT(cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays,readability-redundant-member-init)
+    char* m_end = nullptr;
+    char* m_capacity_end = nullptr;
+};
+/*!
 Input adapter for stdio file access. This adapter read only 1 byte and do not use any
 buffer. This adapter is a very low level adapter.
 */
@@ -209,6 +286,7 @@ class input_stream_adapter
        , token_segment(rhs.token_segment)
        , current_in_get_area(rhs.current_in_get_area)
        , tracking_token(rhs.tracking_token)
+        , no_get_area(rhs.no_get_area)
 #endif
    {
        rhs.is = nullptr;
@@ -295,37 +373,20 @@ class input_stream_adapter
    std::char_traits<char>::int_type get_character()
    {
 #if !JSON_DISABLE_STREAM_BULK_SCAN
-        // sbumpc() refills the get area if it is exhausted
-        const bool refill = streambuf_access::get_ptr(sb) == streambuf_access::get_end(sb);
-        if (JSON_HEDLEY_UNLIKELY(refill))
-        {
-            save_token_segment();
-        }
-#endif
-
-        auto res = sb->sbumpc();
-        // set eof manually, as we don't use the istream interface.
-        if (JSON_HEDLEY_UNLIKELY(res == std::char_traits<char>::eof()))
-        {
-#if !JSON_DISABLE_STREAM_BULK_SCAN
-            current_in_get_area = false;
-#endif
-            is->clear(is->rdstate() | std::ios::eofbit);
-        }
-#if !JSON_DISABLE_STREAM_BULK_SCAN
-        else if (JSON_HEDLEY_UNLIKELY(refill))
-        {
-            // the consumed character is at gptr() - 1, unless the streambuf
-            // has no get area and returned it from uflow()
-            const char* const next = streambuf_access::get_ptr(sb);
-            after_refill(res, next != nullptr && next != streambuf_access::get_begin(sb));
-        }
-        else
+        // the character is in the get area: step over it, as sbumpc() does
+        const char* const next = streambuf_access::get_ptr(sb);
+        if (JSON_HEDLEY_LIKELY(next != streambuf_access::get_end(sb)))
        {
            current_in_get_area = true;
+            streambuf_access::bump(sb, 1);
+            return std::char_traits<char>::to_int_type(*next);
+        }
+        if (no_get_area)
+        {
+            return get_character_no_get_area();
        }
 #endif
-        return res;
+        return get_character_slow();
    }
 #endif

@@ -334,6 +395,18 @@ class input_stream_adapter
    {
 #if JSON_PRECISE_STREAM_POSITION
        commit_lookahead();
+#endif
+#if !JSON_DISABLE_STREAM_BULK_SCAN
+        // the elements are in the get area: copy them, as sgetn() does, but
+        // without the virtual call
+        const char* const first = streambuf_access::get_ptr(sb);
+        const auto available = static_cast<std::size_t>(streambuf_access::get_end(sb) - first);
+        if (JSON_HEDLEY_LIKELY(count * sizeof(T) <= available && count * sizeof(T) <= static_cast<std::size_t>((std::numeric_limits<int>::max)())))
+        {
+            std::memcpy(dest, first, count * sizeof(T));
+            streambuf_access::bump(sb, static_cast<int>(count * sizeof(T)));
+            return count * sizeof(T);
+        }
 #endif
        auto res = static_cast<std::size_t>(sb->sgetn(reinterpret_cast<char*>(dest), static_cast<std::streamsize>(count * sizeof(T))));
        if (JSON_HEDLEY_UNLIKELY(res < count * sizeof(T)))
@@ -421,7 +494,7 @@ class input_stream_adapter
    // last one if @a drop_last.
    void copy_token(std::vector<char>& out, bool drop_last) const
    {
-        out = token_carry;
+        token_carry.copy_to(out);
        if (token_segment != nullptr)
        {
            out.insert(out.end(), token_segment, current_end());
@@ -434,6 +507,47 @@ class input_stream_adapter
 #endif

  private:
+#if !JSON_PRECISE_STREAM_POSITION
+    // the get area is exhausted, or there is none
+#if !JSON_DISABLE_STREAM_BULK_SCAN
+    JSON_HEDLEY_NEVER_INLINE
+#endif
+    std::char_traits<char>::int_type get_character_slow()
+    {
+#if !JSON_DISABLE_STREAM_BULK_SCAN
+        // sbumpc() refills the get area if it is exhausted
+        const bool refill = streambuf_access::get_ptr(sb) == streambuf_access::get_end(sb);
+        if (JSON_HEDLEY_UNLIKELY(refill))
+        {
+            save_token_segment();
+        }
+#endif
+
+        auto res = sb->sbumpc();
+        // set eof manually, as we don't use the istream interface.
+        if (JSON_HEDLEY_UNLIKELY(res == std::char_traits<char>::eof()))
+        {
+#if !JSON_DISABLE_STREAM_BULK_SCAN
+            current_in_get_area = false;
+#endif
+            is->clear(is->rdstate() | std::ios::eofbit);
+        }
+#if !JSON_DISABLE_STREAM_BULK_SCAN
+        else if (JSON_HEDLEY_UNLIKELY(refill))
+        {
+            // the consumed character is at gptr() - 1, unless the streambuf
+            // has no get area and returned it from uflow()
+            const char* const next = streambuf_access::get_ptr(sb);
+            after_refill(res, next != nullptr && next != streambuf_access::get_begin(sb));
+        }
+        else
+        {
+            current_in_get_area = true;
+        }
+#endif
+        return res;
+    }
+#endif
 #if !JSON_DISABLE_STREAM_BULK_SCAN
    // Reads the protected get-area pointers of any std::streambuf. Naming the
    // members through a derived class makes forming the member pointers
@@ -457,6 +571,11 @@ class input_stream_adapter
        {
            (s->*(&streambuf_access::gbump))(n);
        }
+        // sbumpc() for an exhausted get area
+        static std::streambuf::int_type next_character(std::streambuf* s)
+        {
+            return (s->*(&streambuf_access::uflow))();
+        }
    };

    // one past the character last returned by get_character(), if that is in
@@ -477,16 +596,53 @@ class input_stream_adapter
    {
        if (token_segment != nullptr)
        {
-            token_carry.insert(token_carry.end(), token_segment, streambuf_access::get_end(sb));
+            token_carry.append(token_segment, streambuf_access::get_end(sb));
            token_segment = nullptr;
        }
    }

+#if !JSON_PRECISE_STREAM_POSITION
+    // The streambuf has no get area (e.g., std::cin synchronized with stdio):
+    // every character comes from uflow(), and the token is kept by value.
+    JSON_HEDLEY_NEVER_INLINE std::char_traits<char>::int_type get_character_no_get_area()
+    {
+        // the get area is exhausted, so this is what sbumpc() does
+        const auto res = streambuf_access::next_character(sb);
+        if (JSON_HEDLEY_UNLIKELY(res == std::char_traits<char>::eof() || streambuf_access::get_end(sb) != nullptr))
+        {
+            return get_character_no_get_area_other(res);
+        }
+        // current_in_get_area is false: only the first character of a get
+        // area, or the end of the input, is read here
+        if (tracking_token)
+        {
+            token_carry.push_back(std::char_traits<char>::to_char_type(res));
+        }
+        return res;
+    }
+
+    // @a res came from uflow() of a streambuf without a get area: it is the
+    // end of the input, or the streambuf has a get area now
+    JSON_HEDLEY_NEVER_INLINE std::char_traits<char>::int_type get_character_no_get_area_other(std::char_traits<char>::int_type res)
+    {
+        if (res == std::char_traits<char>::eof())
+        {
+            current_in_get_area = false;
+            is->clear(is->rdstate() | std::ios::eofbit);
+            return res;
+        }
+        // the consumed character is at gptr() - 1
+        after_refill(res, streambuf_access::get_ptr(sb) != streambuf_access::get_begin(sb));
+        return res;
+    }
+#endif
+
    // character @a c was just read into a new get area (@a in_get_area) or
    // returned without one
    void after_refill(std::char_traits<char>::int_type c, bool in_get_area)
    {
        current_in_get_area = in_get_area;
+        no_get_area = !in_get_area;
        if (!tracking_token)
        {
            return;
@@ -525,13 +681,16 @@ class input_stream_adapter
 #endif
 #if !JSON_DISABLE_STREAM_BULK_SCAN
    /// the part of the current token that was in earlier get areas
-    std::vector<char> token_carry{}; // NOLINT(readability-redundant-member-init)
+    token_carry_buffer token_carry{}; // NOLINT(readability-redundant-member-init)
    /// start of the current token's part in the get area, or nullptr
    const char* token_segment = nullptr;
    /// whether the character last returned by get_character() is in the get area
    bool current_in_get_area = false;
    /// whether a token is tracked at all; the binary readers never start one
    bool tracking_token = false;
+    /// whether the streambuf had no get area when it was last asked for a
+    /// character
+    bool no_get_area = false;
 #endif
 };
 #endif  // JSON_NO_IO
@@ -12,7 +12,9 @@
 #include <cstddef> // size_t
 #include <cstdint> // uint32_t
 #include <cstdio> // snprintf
+#include <cstring> // memcmp
 #include <initializer_list> // initializer_list
+#include <limits> // numeric_limits
 #include <string> // char_traits, string
 #include <utility> // move
 #include <vector> // vector
@@ -417,30 +419,43 @@ class lexer : public lexer_base<BasicJsonType>
    }

    /// contiguous input: bulk-append the run of ordinary characters and complete
-    /// well-formed UTF-8 sequences starting at the current read position, leaving
-    /// the first byte that needs individual handling (the closing quote, an
-    /// escape, a control character, or an ill-formed UTF-8 byte) for get()
-    void scan_string_bulk(std::true_type /*bulk*/)
+    /// well-formed UTF-8 sequences starting at the current read position, then
+    /// read the first byte that needs individual handling (the closing quote, an
+    /// escape, a control character, or an ill-formed UTF-8 byte) like get().
+    /// That byte is taken from the buffer that was just scanned. Through get(),
+    /// Apple Clang merged this read with the other get() calls of the scan
+    /// function, which load the read position again right after it was stored
+    /// (3% of json::accept() on jeopardy.json on Apple M1).
+    char_int_type get_after_string_run(std::true_type /*bulk*/)
    {
        // a pending unget must be consumed through the normal path first
        if (next_unget)
        {
-            return;
+            return get();
        }
        const std::size_t remaining = ia.bulk_remaining();
        if (remaining == 0)
        {
-            return;
+            return get();
        }
-        const auto* const data = reinterpret_cast<const unsigned char*>(ia.bulk_data());
+        const auto* const raw = ia.bulk_data();
+        const auto* const data = reinterpret_cast<const unsigned char*>(raw);

-        const std::size_t pos = string_bulk_run(data, remaining);
-        if (pos == 0)
+        const std::size_t pos = lexer_string_bulk_run(data, remaining);
+        if (pos != 0)
        {
-            return;
+            token_buffer.append(reinterpret_cast<const typename string_t::value_type*>(data), pos);
+            bulk_consume(reinterpret_cast<const char*>(data), pos);
        }
-        token_buffer.append(reinterpret_cast<const typename string_t::value_type*>(data), pos);
-        bulk_consume(reinterpret_cast<const char*>(data), pos);
+        if (pos == remaining)
+        {
+            return get(); // end of the contiguous input
+        }
+        // what get() does, with the byte at hand
+        advance_position();
+        ia.bulk_skip(1);
+        current = char_traits<char_type>::to_int_type(raw[pos]);
+        return track_after_read();
    }

    /// consume @a n characters at @a data (the adapter's bulk_data()) and do
@@ -473,7 +488,10 @@ class lexer : public lexer_base<BasicJsonType>
    }

    /// streaming input: no bulk fast path
-    void scan_string_bulk(std::false_type /*bulk*/) const noexcept {}
+    char_int_type get_after_string_run(std::false_type /*bulk*/)
+    {
+        return get();
+    }

    /*!
    @brief scan a string literal
@@ -501,11 +519,8 @@ class lexer : public lexer_base<BasicJsonType>
        while (true)
        {
            // bulk-consume ordinary characters from contiguous input, then
-            // handle the next special byte through the switch below
-            scan_string_bulk(std::integral_constant<bool, bulk_scan> {});
-
-            // get the next character
-            switch (get())
+            // get the next character, the one that ends the run
+            switch (get_after_string_run(std::integral_constant<bool, bulk_scan>()))
            {
                // end of file while parsing the string
                case char_traits<char_type>::eof():
@@ -1625,9 +1640,12 @@ scan_number_done:
        const std::size_t avail = rem + 1;

        // validate + classify the number extent (mirrors scan_number()'s grammar)
+        // and accumulate the mantissa digits on the way, so that tokens with up
+        // to 19 digits need no second pass for their value
        std::size_t i = 0;
        std::size_t dot_index = std::string::npos;
        token_type number_type = token_type::value_unsigned;
+        std::uint64_t w = 0;
        if (data[0] == '-')
        {
            number_type = token_type::value_integer;
@@ -1637,22 +1655,21 @@ scan_number_done:
                return token_type::uninitialized;
            }
        }
+        const std::size_t integer_begin = i;
        if (data[i] == '0')
        {
            ++i;
        }
        else if (data[i] >= '1' && data[i] <= '9')
        {
-            ++i;
-            while (i < avail && data[i] >= '0' && data[i] <= '9')
-            {
-                ++i;
-            }
+            i = accumulate_digits(data, i, avail, w);
        }
        else
        {
            return token_type::uninitialized;
        }
+        std::size_t digit_count = i - integer_begin;
+        std::size_t fraction_digits = 0;
        if (i < avail && data[i] == '.')
        {
            number_type = token_type::value_float;
@@ -1662,29 +1679,39 @@ scan_number_done:
            {
                return token_type::uninitialized;
            }
-            while (i < avail && data[i] >= '0' && data[i] <= '9')
-            {
-                ++i;
-            }
+            const std::size_t fraction_begin = i;
+            i = accumulate_digits(data, i, avail, w);
+            fraction_digits = i - fraction_begin;
+            digit_count += fraction_digits;
        }
        // the mantissa ends here, whether or not an exponent part follows
        const std::size_t mantissa_end = i;
+        std::int64_t exponent = 0;
        if (i < avail && (data[i] == 'e' || data[i] == 'E'))
        {
            number_type = token_type::value_float;
            ++i;
+            bool negative_exponent = false;
            if (i < avail && (data[i] == '+' || data[i] == '-'))
            {
+                negative_exponent = data[i] == '-';
                ++i;
            }
            if (i >= avail || !(data[i] >= '0' && data[i] <= '9'))
            {
                return token_type::uninitialized;
            }
+            // saturated far beyond every range, see parse_float_exponent()
+            constexpr std::int64_t saturation = 100000000000000000; // 10^17
            while (i < avail && data[i] >= '0' && data[i] <= '9')
            {
+                if (exponent < saturation)
+                {
+                    exponent = (exponent * 10) + (data[i] - '0');
+                }
                ++i;
            }
+            exponent = negative_exponent ? -exponent : exponent;
        }
        const std::size_t len = i;
        if (number_may_continue(len == avail, std::integral_constant<bool, bulk_window> {}))
@@ -1705,7 +1732,10 @@ scan_number_done:
 #if !JSON_DIAGNOSTIC_POSITIONS
        if (number_type != token_type::value_float)
        {
-            const token_type integer_result = convert_integer(number_type, data, data + len);
+            // up to 18 digits always fit into std::uint64_t and std::int64_t
+            const token_type integer_result = (digit_count <= 18)
+                                              ? store_integer(number_type, w)
+                                              : convert_integer(number_type, data, data + len);
            if (JSON_HEDLEY_LIKELY(integer_result != token_type::uninitialized))
            {
                bulk_consume(data + 1, len - 1);
@@ -1719,15 +1749,42 @@ scan_number_done:
        }
 #endif

-        // materialize the token exactly as scan_number() would. reset() already
-        // cleared token_buffer, so append() fills it (assign() is avoided
-        // because custom string_t types need not provide it)
-        token_buffer.append(reinterpret_cast<const typename string_t::value_type*>(data), len);
        decimal_point_position = dot_index;

        bulk_consume(data + 1, len - 1);
        read_number_terminator(std::integral_constant<bool, bulk_window> {});

+        // a float whose digits all fit into w converts from the accumulated
+        // value; longer ones (and other float formats) take the general path
+        if (number_type == token_type::value_float && digit_count <= 19)
+        {
+            float_significand s;
+            s.w = w;
+            s.exponent = exponent - static_cast<std::int64_t>(fraction_digits);
+            s.negative = data[0] == '-';
+            if (convert_accumulated_float(s, std::integral_constant<bool, has_native_float_format<number_float_t>::value> {}))
+            {
+                // the token text is only copied into token_buffer when
+                // get_string() asks for it; the library's own SAX handlers
+                // ignore it. A window into a stream may be refilled by the
+                // next read, so there the text is copied right away.
+                if (bulk_window)
+                {
+                    token_buffer.append(reinterpret_cast<const typename string_t::value_type*>(data), len);
+                }
+                else
+                {
+                    pending_number_text = data;
+                    pending_number_length = len;
+                }
+                return token_type::value_float;
+            }
+        }
+
+        // materialize the token exactly as scan_number() would. reset() already
+        // cleared token_buffer, so append() fills it (assign() is avoided
+        // because custom string_t types need not provide it)
+        token_buffer.append(reinterpret_cast<const typename string_t::value_type*>(data), len);
        return convert_number(number_type, mantissa_end);
    }

@@ -1756,6 +1813,44 @@ scan_number_done:
    /// the input is not handed back, so the terminator can stay unread
    void read_number_terminator(std::false_type /*window*/) const noexcept {}

+    /// binary32/binary64: the value of a float token from its accumulated
+    /// significand (see scan_number_bulk_contiguous())
+    bool convert_accumulated_float(const float_significand& s, std::true_type /*native*/) noexcept
+    {
+        // accept() only needs to know that the value is finite (see the parser):
+        // w < 10^19, so a value below 10^max_exponent10 cannot overflow, and a
+        // value that underflows is a finite number as well. Only a token that
+        // may overflow has to be converted to find out.
+        if (JSON_HEDLEY_UNLIKELY(discard_number_values && s.exponent + 19 <= std::numeric_limits<number_float_t>::max_exponent10))
+        {
+            value_float = 0;
+            return true;
+        }
+        value_float = decimal_to_float<number_float_t>(s);
+        return true;
+    }
+
+    /// other formats (e.g. x87 long double): not instantiated for them, as
+    /// decimal_to_float() only supports binary32/binary64
+    static bool convert_accumulated_float(const float_significand& /*s*/, std::false_type /*native*/) noexcept
+    {
+        return false;
+    }
+
+    /// the value of an integer token with at most 18 digits, accumulated in @a w
+    token_type store_integer(token_type number_type, std::uint64_t w) noexcept
+    {
+        if (number_type == token_type::value_unsigned)
+        {
+            value_unsigned = static_cast<number_unsigned_t>(w);
+            // reject values that do not round-trip into a narrower type
+            return (static_cast<std::uint64_t>(value_unsigned) == w) ? token_type::value_unsigned : token_type::uninitialized;
+        }
+        const std::int64_t x = -static_cast<std::int64_t>(w);
+        value_integer = static_cast<number_integer_t>(x);
+        return (static_cast<std::int64_t>(value_integer) == x) ? token_type::value_integer : token_type::uninitialized;
+    }
+
    /// contiguous input: try the number fast path, else the byte-path scanner
    token_type scan_number_dispatch(std::true_type /*bulk*/)
    {
@@ -1770,18 +1865,23 @@ scan_number_done:
    }

    /*!
-    @param[in] literal_text  the literal text to expect
-    @param[in] length        the length of the passed literal text
-    @param[in] return_type   the token type to return on success
+    @param[in] rest         the literal text after its first character, which
+                            is current (its length is a template parameter, so
+                            that the comparison of the contiguous fast path is
+                            a fixed-size load, not a call of memcmp)
+    @param[in] return_type  the token type to return on success
    */
-    JSON_HEDLEY_NON_NULL(2)
-    token_type scan_literal(const char_type* literal_text, const std::size_t length,
-                            token_type return_type)
+    template<std::size_t N>
+    JSON_HEDLEY_NEVER_INLINE token_type scan_literal(const char (&rest)[N], token_type return_type) // NOLINT(cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays)
    {
-        JSON_ASSERT(char_traits<char_type>::to_char_type(current) == literal_text[0]);
-        for (std::size_t i = 1; i < length; ++i)
+        constexpr std::size_t length = N - 1;
+        if (scan_literal_bulk(rest, length, std::integral_constant<bool, bulk_scan> {}))
        {
-            if (JSON_HEDLEY_UNLIKELY(char_traits<char_type>::to_char_type(get()) != literal_text[i]))
+            return return_type;
+        }
+        for (std::size_t i = 0; i < length; ++i)
+        {
+            if (JSON_HEDLEY_UNLIKELY(char_traits<char_type>::to_char_type(get()) != static_cast<char_type>(rest[i])))
            {
                error_message = "invalid literal";
                return token_type::parse_error;
@@ -1790,6 +1890,27 @@ scan_number_done:
        return return_type;
    }

+    /// contiguous input: compare the rest of a literal at once; false (and
+    /// nothing consumed) if it does not match, so that the byte path reports
+    /// the error at the right character
+    JSON_HEDLEY_ALWAYS_INLINE bool scan_literal_bulk(const char* rest, const std::size_t length, std::true_type /*bulk*/)
+    {
+        if (next_unget || ia.bulk_remaining() < length
+                || std::memcmp(ia.bulk_data(), rest, length) != 0)
+        {
+            return false;
+        }
+        bulk_consume(reinterpret_cast<const char*>(ia.bulk_data()), length);
+        current = static_cast<char_int_type>(static_cast<unsigned char>(rest[length - 1]));
+        return true;
+    }
+
+    /// streaming input: no bulk fast path
+    bool scan_literal_bulk(const char* /*rest*/, const std::size_t /*length*/, std::false_type /*bulk*/) const noexcept
+    {
+        return false;
+    }
+
    /////////////////////
    // input management
    /////////////////////
@@ -1798,6 +1919,7 @@ scan_number_done:
    void reset() noexcept
    {
        token_buffer.clear();
+        pending_number_text = nullptr;
        decimal_point_position = std::string::npos;

 #if JSON_DIAGNOSTIC_POSITIONS
@@ -2057,10 +2179,30 @@ scan_number_done:
    /// return current string value
    string_t& get_string()
    {
+        if (pending_number_text != nullptr)
+        {
+            token_buffer.append(reinterpret_cast<const typename string_t::value_type*>(pending_number_text), pending_number_length);
+            pending_number_text = nullptr;
+        }
        // a number token holds '.' regardless of the locale (#4084)
        return token_buffer;
    }

+    /// the value of a string token (key or string), which never has pending
+    /// number text, so get_string()'s check is not needed
+    string_t& get_string_token() noexcept
+    {
+        JSON_ASSERT(pending_number_text == nullptr);
+        return token_buffer;
+    }
+
+    /// the text of a float token for a SAX handler that ignores it (the
+    /// library's own handlers): empty, without copying the token
+    const string_t& get_ignored_number_text() const noexcept
+    {
+        return token_buffer;
+    }
+
    /////////////////////
    // diagnostics
    /////////////////////
@@ -2394,21 +2536,14 @@ scan_number_done:
                return token_type::value_separator;

            // literals
+            // (the text after the first character; no local arrays, which
+            // would give this function a stack canary on every token)
            case 't':
-            {
-                std::array<char_type, 4> true_literal = {{static_cast<char_type>('t'), static_cast<char_type>('r'), static_cast<char_type>('u'), static_cast<char_type>('e')}};
-                return scan_literal(true_literal.data(), true_literal.size(), token_type::literal_true);
-            }
+                return scan_literal("rue", token_type::literal_true);
            case 'f':
-            {
-                std::array<char_type, 5> false_literal = {{static_cast<char_type>('f'), static_cast<char_type>('a'), static_cast<char_type>('l'), static_cast<char_type>('s'), static_cast<char_type>('e')}};
-                return scan_literal(false_literal.data(), false_literal.size(), token_type::literal_false);
-            }
+                return scan_literal("alse", token_type::literal_false);
            case 'n':
-            {
-                std::array<char_type, 4> null_literal = {{static_cast<char_type>('n'), static_cast<char_type>('u'), static_cast<char_type>('l'), static_cast<char_type>('l')}};
-                return scan_literal(null_literal.data(), null_literal.size(), token_type::literal_null);
-            }
+                return scan_literal("ull", token_type::literal_null);

            // string
            case '\"':
@@ -2456,6 +2591,11 @@ scan_number_done:
    /// whether the next get() call should just return current
    bool next_unget = false;

+    /// the text of the current float token in the input, not yet copied into
+    /// token_buffer (see get_string()), or nullptr
+    const char* pending_number_text = nullptr;
+    std::size_t pending_number_length = 0;
+
    /// the start position of the current token
    position_t position {};

@@ -16,7 +16,6 @@
 #include <cstddef> // size_t
 #include <cstdint> // int64_t, uint64_t
 #include <cstdlib> // strtof, strtod, strtold
-#include <cstring> // memcpy
 #include <limits> // numeric_limits
 #include <string> // string
 #include <type_traits> // conditional, integral_constant, is_signed, true_type, false_type
@@ -275,13 +274,77 @@ JSON_HEDLEY_ALWAYS_INLINE std::uint32_t parse_eight_digits(std::uint64_t v) noex
    return static_cast<std::uint32_t>(((v & 0x0000FFFF0000FFFFu) * 42949672960001u) >> 32u);
 }

-/// whether [first, last) contains a digit other than '0'
-inline bool has_nonzero_digit(const char* first, const char* last) noexcept
+/// whether the eight bytes in @a v (see read_eight_bytes()) are all ASCII
+/// digits (after fast_float)
+JSON_HEDLEY_ALWAYS_INLINE bool is_eight_digits(std::uint64_t v) noexcept
 {
-    return std::any_of(first, last, [](char c) noexcept
+    return ((v & 0xF0F0F0F0F0F0F0F0u) | (((v + 0x0606060606060606u) & 0xF0F0F0F0F0F0F0F0u) >> 4u)) == 0x3333333333333333u;
+}
+
+/*!
+@brief skip the ASCII digits starting at data[i] and accumulate their value
+
+Eight digits are taken at a time while at least eight bytes remain. @a w wraps
+around after 19 digits; the caller only uses it for shorter digit runs.
+
+@return the index of the first byte at or after @a i that is not a digit
+*/
+JSON_HEDLEY_ALWAYS_INLINE std::size_t accumulate_digits(const char* data, std::size_t i, std::size_t avail, std::uint64_t& w) noexcept
+{
+    while (avail - i >= 8)
    {
-        return c != '0';
-    });
+        const std::uint64_t v = read_eight_bytes(data + i);
+        if (!is_eight_digits(v))
+        {
+            break;
+        }
+        w = (w * 100000000u) + parse_eight_digits(v);
+        i += 8;
+    }
+    while (i < avail && data[i] >= '0' && data[i] <= '9')
+    {
+        w = (w * 10u) + static_cast<std::uint64_t>(data[i] - '0');
+        ++i;
+    }
+    return i;
+}
+
+/// whether [first, last) contains a digit other than '0'; a plain loop, as
+/// GCC calls std::any_of out of line even for the usual empty range
+JSON_HEDLEY_ALWAYS_INLINE bool has_nonzero_digit(const char* first, const char* last) noexcept
+{
+    for (; first != last; ++first)
+    {
+        if (*first != '0')
+        {
+            return true;
+        }
+    }
+    return false;
+}
+
+/*!
+@brief accumulate the validated digits [p, last) into @a w, as long as
+       @a remaining digits still fit into it
+
+Eight digits are taken at a time while at least eight remain, and @a remaining
+is decreased by the number of digits taken.
+
+@return a pointer past the last digit taken
+*/
+JSON_HEDLEY_ALWAYS_INLINE const char* accumulate_significant_digits(const char* p, const char* last, int& remaining, std::uint64_t& w) noexcept
+{
+    while (remaining >= 8 && last - p >= 8)
+    {
+        w = (w * 100000000u) + parse_eight_digits(read_eight_bytes(p));
+        p += 8;
+        remaining -= 8;
+    }
+    for (; remaining > 0 && p != last; ++p, --remaining)
+    {
+        w = (w * 10u) + static_cast<std::uint64_t>(*p - '0');
+    }
+    return p;
 }

 /// the value of the validated exponent digits [+-]?[0-9]+ in [first, last),
@@ -327,7 +390,7 @@ truncated is set.
                                   std::string::npos if there is none
@param[in] mantissa_end            index of the 'e'/'E', or the token length
 */
-inline float_significand parse_float_significand(const char* first, const char* last,
+JSON_HEDLEY_ALWAYS_INLINE float_significand parse_float_significand(const char* first, const char* last,
        std::size_t decimal_point_position, std::size_t mantissa_end) noexcept
 {
    float_significand s;
@@ -342,16 +405,7 @@ inline float_significand parse_float_significand(const char* first, const char*
    int remaining = 19; // digits that still fit into w
    if (*p != '0') // the integer part is "0" or [1-9][0-9]*
    {
-        while (remaining >= 8 && integer_last - p >= 8)
-        {
-            w = (w * 100000000u) + parse_eight_digits(read_eight_bytes(p));
-            p += 8;
-            remaining -= 8;
-        }
-        for (; remaining > 0 && p != integer_last; ++p, --remaining)
-        {
-            w = (w * 10u) + static_cast<std::uint64_t>(*p - '0');
-        }
+        p = accumulate_significant_digits(p, integer_last, remaining, w);
        s.exponent = integer_last - p;
        s.truncated = has_nonzero_digit(p, integer_last);
    }
@@ -370,16 +424,7 @@ inline float_significand parse_float_significand(const char* first, const char*
            s.exponent -= p - zeros;
        }
        const char* const digits = p;
-        while (remaining >= 8 && mantissa_last - p >= 8)
-        {
-            w = (w * 100000000u) + parse_eight_digits(read_eight_bytes(p));
-            p += 8;
-            remaining -= 8;
-        }
-        for (; remaining > 0 && p != mantissa_last; ++p, --remaining)
-        {
-            w = (w * 10u) + static_cast<std::uint64_t>(*p - '0');
-        }
+        p = accumulate_significant_digits(p, mantissa_last, remaining, w);
        s.exponent -= p - digits;
        s.truncated = s.truncated || has_nonzero_digit(p, mantissa_last);
    }
@@ -712,15 +757,14 @@ std::uint64_t digit_comparison(const char* first, const char* last, std::uint64_
 inline void float_from_bits(std::uint64_t bits, double& value) noexcept
 {
    static_assert(sizeof(double) == sizeof(std::uint64_t), "double must have 64 bits");
-    std::memcpy(&value, &bits, sizeof(value));
+    value = bit_cast<double>(bits);
 }

 /// the float with the IEEE-754 bits @a bits (the lower 32)
 inline void float_from_bits(std::uint64_t bits, float& value) noexcept
 {
    static_assert(sizeof(float) == sizeof(std::uint32_t), "float must have 32 bits");
-    const auto bits32 = static_cast<std::uint32_t>(bits);
-    std::memcpy(&value, &bits32, sizeof(bits32));
+    value = bit_cast<float>(static_cast<std::uint32_t>(bits));
 }

 /// the powers of ten that are exact in binary64 (up to 10^22)
@@ -51,6 +51,20 @@ template<typename BasicJsonType>
 using parser_callback_t =
    std::function<bool(int /*depth*/, parse_event_t /*event*/, BasicJsonType& /*parsed*/)>;

+/// whether a SAX handler ignores the text of float tokens (the library's own
+/// handlers do), so that the parser need not materialize it
+template<typename SAX>
+struct sax_ignores_number_text : std::false_type {};
+
+template<typename BasicJsonType, typename InputAdapterType, bool Collect>
+struct sax_ignores_number_text<json_sax_dom_parser<BasicJsonType, InputAdapterType, Collect>> : std::true_type {};
+
+template<typename BasicJsonType, typename InputAdapterType>
+struct sax_ignores_number_text<json_sax_dom_callback_parser<BasicJsonType, InputAdapterType>> : std::true_type {};
+
+template<typename BasicJsonType>
+struct sax_ignores_number_text<json_sax_acceptor<BasicJsonType>> : std::true_type {};
+
 /*!
@brief syntax analysis

@@ -117,7 +131,7 @@ class parser
        }
        else
        {
-            json_sax_dom_parser<BasicJsonType, InputAdapterType> sdp(result, allow_exceptions, &m_lexer);
+            json_sax_dom_parser<BasicJsonType, InputAdapterType, true> sdp(result, allow_exceptions, &m_lexer);

            // in case of an error, return a discarded value
            if (!parse_dom(sdp, strict))
@@ -171,6 +185,23 @@ class parser
    }

  private:
+    /// the text of the current float token for @a sax (see sax_ignores_number_text)
+    template<typename SAX>
+    const string_t& number_float_text(SAX* /*sax*/)
+    {
+        return number_float_text(std::integral_constant<bool, sax_ignores_number_text<SAX>::value> {});
+    }
+
+    const string_t& number_float_text(std::true_type /*ignored*/) const noexcept
+    {
+        return m_lexer.get_ignored_number_text();
+    }
+
+    string_t& number_float_text(std::false_type /*ignored*/)
+    {
+        return m_lexer.get_string();
+    }
+
    /*!
    @brief run a DOM SAX parser to completion and position the lexer

@@ -212,12 +243,20 @@ class parser
    JSON_HEDLEY_NON_NULL(2)
    bool sax_parse_internal(SAX* sax)
    {
-        // stack to remember the hierarchy of structured values we are parsing
-        // true = array; false = object
-        std::vector<bool> states;
        // value to avoid a goto (see comment where set to true)
        bool skip_to_state_evaluation = false;

+        // stack to remember the hierarchy of structured values we are parsing
+        // true = array; false = object (bytes, not std::vector<bool>, whose
+        // push_back() is a call with GCC)
+        std::vector<std::uint8_t> states;
+        // a document that starts with a container pushes onto the stack at
+        // once: allocate it in one step instead of growing it from 1 byte
+        if (last_token == token_type::begin_object || last_token == token_type::begin_array)
+        {
+            states.reserve(32);
+        }
+
        while (true)
        {
            if (!skip_to_state_evaluation)
@@ -247,7 +286,7 @@ class parser
                        {
                            return syntax_error(*sax, exception_message(token_type::value_string, "object key"));
                        }
-                        if (JSON_HEDLEY_UNLIKELY(!sax->key(m_lexer.get_string())))
+                        if (JSON_HEDLEY_UNLIKELY(!sax->key(m_lexer.get_string_token())))
                        {
                            return false;
                        }
@@ -259,7 +298,7 @@ class parser
                        }

                        // remember we are now inside an object
-                        states.push_back(false);
+                        states.push_back(0);

                        // parse values
                        get_token();
@@ -284,7 +323,7 @@ class parser
                        }

                        // remember we are now inside an array
-                        states.push_back(true);
+                        states.push_back(1);

                        // parse values (no need to call get_token)
                        continue;
@@ -301,7 +340,7 @@ class parser
                                                    out_of_range::create(exception_id::number_overflow, concat("number overflow parsing '", m_lexer.get_token_string(), '\''), nullptr));
                        }

-                        if (JSON_HEDLEY_UNLIKELY(!sax->number_float(res, m_lexer.get_string())))
+                        if (JSON_HEDLEY_UNLIKELY(!sax->number_float(res, number_float_text(sax))))
                        {
                            return false;
                        }
@@ -347,7 +386,7 @@ class parser

                    case token_type::value_string:
                    {
-                        if (JSON_HEDLEY_UNLIKELY(!sax->string(m_lexer.get_string())))
+                        if (JSON_HEDLEY_UNLIKELY(!sax->string(m_lexer.get_string_token())))
                        {
                            return false;
                        }
@@ -401,7 +440,7 @@ class parser
                return true;
            }

-            if (states.back())  // array
+            if (states.back() != 0)  // array
            {
                // comma -> next value
                // or end of array (ignore_trailing_commas = true)
@@ -456,7 +495,7 @@ class parser
                        return syntax_error(*sax, exception_message(token_type::value_string, "object key"));
                    }

-                    if (JSON_HEDLEY_UNLIKELY(!sax->key(m_lexer.get_string())))
+                    if (JSON_HEDLEY_UNLIKELY(!sax->key(m_lexer.get_string_token())))
                    {
                        return false;
                    }
@@ -0,0 +1,321 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++
+// |  |  |__   |  |  | | | |  version 3.12.0
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
+// SPDX-FileCopyrightText: 2018-2025 The simdjson authors <https://github.com/simdjson/simdjson>
+// SPDX-License-Identifier: MIT
+
+#pragma once
+
+#include <array> // array
+#include <atomic> // atomic
+#include <cstddef> // size_t
+#include <cstdint> // uint8_t, uint64_t
+
+#include <nlohmann/detail/bit_ops.hpp>
+#include <nlohmann/detail/macro_scope.hpp>
+
+// Vector code for runs of string bytes, used by the lexer for contiguous input
+// (see string_bulk_run()). NEON (AArch64) and SSE2 (x86-64) belong to the
+// baseline instruction sets and are used by default. The vector UTF-8 check
+// needs NEON or SSSE3. SSSE3 is not part of x86-64, and the code must not
+// depend on the flags of a translation unit (two translation units with
+// different flags would have different definitions of the same inline
+// functions): the check is compiled for SSSE3 with a function attribute and
+// used where the CPU has SSSE3 (all x86-64 CPUs since about 2011), else the
+// portable check. Code compiled for SSSE3 anyway (-mssse3 or more) skips the
+// CPU check. JSON_NO_SIMD selects the portable code everywhere.
+// NLOHMANN_JSON_NO_TARGET_ATTRIBUTE (for compilers that ignore the target
+// attribute and then reject the SSSE3 intrinsics) keeps the check portable
+// without disabling the SSE2 code.
+#if !defined(JSON_NO_SIMD) && defined(__aarch64__) && (defined(__GNUC__) || defined(__clang__)) && defined(__BYTE_ORDER__) && defined(__ORDER_LITTLE_ENDIAN__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+    #include <arm_neon.h>
+    #define JSON_SCAN_NEON 1
+#else
+    #define JSON_SCAN_NEON 0
+#endif
+// (x86 only: other targets can define __SSE2__ as well, e.g., WebAssembly with -msse2, but have no <cpuid.h>)
+#if !defined(JSON_NO_SIMD) && !JSON_SCAN_NEON && (defined(__x86_64__) || defined(__i386__) || defined(_M_X64) || defined(_M_IX86)) && !defined(_M_ARM64EC) && (defined(__SSE2__) || defined(_M_X64) || (defined(_M_IX86_FP) && _M_IX86_FP >= 2))
+    #include <emmintrin.h>
+    #define JSON_SCAN_SSE2 1
+#else
+    #define JSON_SCAN_SSE2 0
+#endif
+#if JSON_SCAN_SSE2 && defined(__SSSE3__)
+    #include <tmmintrin.h>
+    #define JSON_SCAN_SSSE3 1 // NOLINT(cppcoreguidelines-macro-to-enum,modernize-macro-to-enum)
+#else
+    #define JSON_SCAN_SSSE3 0 // NOLINT(cppcoreguidelines-macro-to-enum,modernize-macro-to-enum)
+#endif
+#if JSON_SCAN_SSE2 && !JSON_SCAN_SSSE3 && !defined(NLOHMANN_JSON_NO_TARGET_ATTRIBUTE) && ((defined(__clang__) && __clang_major__ >= 4) || (defined(__GNUC__) && !defined(__clang__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)) && !defined(__cpp_modules)))
+    // (GCC before 4.9 has no SSSE3 intrinsics without -mssse3; GCC with C++20
+    // modules drops the target attribute from functions it reads from a module
+    // interface and then rejects the intrinsics: "needs isa option -mssse3")
+    // <cpuid.h> of GCC before 11 has no include guard, and json.hpp and
+    // json_view.hpp both include it
+    #ifndef NLOHMANN_JSON_CPUID_INCLUDED
+        #define NLOHMANN_JSON_CPUID_INCLUDED
+        #include <cpuid.h>
+    #endif
+    #include <tmmintrin.h>
+    #define JSON_SCAN_SSSE3_DISPATCH 1 // NOLINT(cppcoreguidelines-macro-to-enum,modernize-macro-to-enum)
+    #define JSON_SCAN_SSSE3_TARGET __attribute__((target("ssse3")))
+#elif JSON_SCAN_SSE2 && !JSON_SCAN_SSSE3 && defined(_MSC_VER)
+    // (MSVC compiles intrinsics of any instruction set)
+    #include <intrin.h>
+    #include <tmmintrin.h>
+    #define JSON_SCAN_SSSE3_DISPATCH 1 // NOLINT(cppcoreguidelines-macro-to-enum,modernize-macro-to-enum)
+    #define JSON_SCAN_SSSE3_TARGET
+#else
+    #define JSON_SCAN_SSSE3_DISPATCH 0 // NOLINT(cppcoreguidelines-macro-to-enum,modernize-macro-to-enum)
+    #define JSON_SCAN_SSSE3_TARGET
+#endif
+#define JSON_SCAN_VECTOR (JSON_SCAN_NEON || JSON_SCAN_SSE2)
+#define JSON_SCAN_VECTOR_UTF8 (JSON_SCAN_NEON || JSON_SCAN_SSSE3 || JSON_SCAN_SSSE3_DISPATCH)
+
+NLOHMANN_JSON_NAMESPACE_BEGIN
+namespace detail
+{
+
+#if JSON_SCAN_VECTOR
+/*!
+@brief the first byte of a string run that is a quote, a backslash, a control
+character, or not ASCII, 16 bytes per step
+
+Stops at such a byte, or where fewer than 16 bytes are left (the caller tells
+the two apart). A signed compare with 0x20 finds control characters and
+non-ASCII bytes at once.
+*/
+JSON_HEDLEY_ALWAYS_INLINE const unsigned char* vector_plain_run(const unsigned char* p, const unsigned char* e) noexcept
+{
+    while (e - p >= 16)
+    {
+#if JSON_SCAN_NEON
+        const uint8x16_t in = vld1q_u8(p);
+        const uint8x16_t special = vorrq_u8(vorrq_u8(vceqq_u8(in, vdupq_n_u8('"')), vceqq_u8(in, vdupq_n_u8('\\'))),
+                                            vcltq_s8(vreinterpretq_s8_u8(in), vdupq_n_s8(0x20)));
+        // one nibble per byte (the usual NEON replacement of x86's movemask, see
+        // D. Kutenin, "Porting x86 vector bitmask optimizations to Arm NEON", 2022)
+        const std::uint64_t bits = vget_lane_u64(vreinterpret_u64_u8(vshrn_n_u16(vreinterpretq_u16_u8(special), 4)), 0);
+        if (bits != 0)
+        {
+            return p + (count_trailing_zeros(bits) >> 2u);
+        }
+#else
+        const __m128i in = _mm_loadu_si128(static_cast<const __m128i*>(static_cast<const void*>(p))); // NOLINT(bugprone-casting-through-void)
+        const __m128i special = _mm_or_si128(_mm_or_si128(_mm_cmpeq_epi8(in, _mm_set1_epi8('"')), _mm_cmpeq_epi8(in, _mm_set1_epi8('\\'))),
+                                             _mm_cmplt_epi8(in, _mm_set1_epi8(0x20)));
+        const auto bits = static_cast<std::uint64_t>(static_cast<unsigned>(_mm_movemask_epi8(special)));
+        if (bits != 0)
+        {
+            return p + count_trailing_zeros(bits);
+        }
+#endif
+        p += 16;
+    }
+    return p;
+}
+#endif
+
+#if JSON_SCAN_VECTOR
+/// vector_plain_run() for runs that are already longer than a few words:
+/// inline with SSE2, out of line with NEON, where a larger string loop slows
+/// down the rest of the lexer
+#if JSON_SCAN_NEON
+    JSON_HEDLEY_NEVER_INLINE inline
+#else
+    JSON_HEDLEY_ALWAYS_INLINE
+#endif
+const unsigned char* vector_plain_run_long(const unsigned char* p, const unsigned char* e) noexcept
+{
+    return vector_plain_run(p, e);
+}
+#endif
+
+#if JSON_SCAN_SSSE3_DISPATCH
+/// whether the CPU has SSSE3 (CPUID leaf 1, ECX bit 9)
+inline bool cpu_ssse3() noexcept
+{
+#if defined(_MSC_VER) && !defined(__clang__)
+    std::array<int, 4> regs {{}};
+    __cpuid(regs.data(), 1);
+    return (static_cast<unsigned>(regs[2]) & (1u << 9u)) != 0;
+#else
+    unsigned eax = 0;
+    unsigned ebx = 0;
+    unsigned ecx = 0;
+    unsigned edx = 0;
+    return __get_cpuid(1, &eax, &ebx, &ecx, &edx) != 0 && (ecx & (1u << 9u)) != 0;
+#endif
+}
+
+/// whether the CPU has SSSE3, asked once: the answer is kept in an atomic
+/// that is initialized at compile time, so that neither a guard of a local
+/// static nor a global constructor is needed (threads that ask at the same
+/// time all store the same answer)
+JSON_HEDLEY_ALWAYS_INLINE bool cpu_has_ssse3() noexcept
+{
+    static std::atomic<int> known{0}; // 0: not asked yet, 1: no, 2: yes
+    int state = known.load(std::memory_order_relaxed);
+    if (JSON_HEDLEY_UNLIKELY(state == 0))
+    {
+        state = cpu_ssse3() ? 2 : 1;
+        known.store(state, std::memory_order_relaxed);
+    }
+    return state == 2;
+}
+#endif
+
+#if JSON_SCAN_VECTOR_UTF8
+/// Tables of the UTF-8 check of J. Keiser and D. Lemire, "Validating UTF-8 In
+/// Less Than One Instruction Per Byte" (2021), as in simdjson ("lookup4"): each
+/// maps a nibble (high and low nibble of the previous byte, high nibble of the
+/// current byte) to the errors it allows; a byte pair is ill-formed if all
+/// three have an error bit in common.
+template<typename Dummy = void>
+struct utf8_lookup4
+{
+    static constexpr std::uint8_t too_short = 1u << 0u, too_long = 1u << 1u, overlong_3 = 1u << 2u, too_large = 1u << 3u;
+    static constexpr std::uint8_t surrogate = 1u << 4u, overlong_2 = 1u << 5u, too_large_1000 = 1u << 6u, overlong_4 = 1u << 6u;
+    static constexpr std::uint8_t two_conts = 1u << 7u, carry = too_short | too_long | two_conts;
+    static const std::array<std::uint8_t, 16> byte_1_high;
+    static const std::array<std::uint8_t, 16> byte_1_low;
+    static const std::array<std::uint8_t, 16> byte_2_high;
+};
+
+template<typename Dummy>
+const std::array<std::uint8_t, 16> utf8_lookup4<Dummy>::byte_1_high =
+{
+    {
+        too_long, too_long, too_long, too_long, too_long, too_long, too_long, too_long,
+        two_conts, two_conts, two_conts, two_conts,
+        too_short | overlong_2, too_short, too_short | overlong_3 | surrogate, too_short | too_large | too_large_1000 | overlong_4
+    }
+};
+
+template<typename Dummy>
+const std::array<std::uint8_t, 16> utf8_lookup4<Dummy>::byte_1_low =
+{
+    {
+        carry | overlong_3 | overlong_2 | overlong_4, carry | overlong_2, carry, carry,
+        carry | too_large, carry | too_large | too_large_1000, carry | too_large | too_large_1000, carry | too_large | too_large_1000,
+        carry | too_large | too_large_1000, carry | too_large | too_large_1000, carry | too_large | too_large_1000, carry | too_large | too_large_1000,
+        carry | too_large | too_large_1000, carry | too_large | too_large_1000 | surrogate, carry | too_large | too_large_1000, carry | too_large | too_large_1000
+    }
+};
+
+template<typename Dummy>
+const std::array<std::uint8_t, 16> utf8_lookup4<Dummy>::byte_2_high =
+{
+    {
+        too_short, too_short, too_short, too_short, too_short, too_short, too_short, too_short,
+        static_cast<std::uint8_t>(too_long | overlong_2 | two_conts | overlong_3 | too_large_1000 | overlong_4),
+        static_cast<std::uint8_t>(too_long | overlong_2 | two_conts | overlong_3 | too_large),
+        static_cast<std::uint8_t>(too_long | overlong_2 | two_conts | surrogate | too_large),
+        static_cast<std::uint8_t>(too_long | overlong_2 | two_conts | surrogate | too_large),
+        too_short, too_short, too_short, too_short
+    }
+};
+
+/*!
+@brief the run of plain string bytes and well-formed UTF-8 at p (a character
+       boundary), 16 bytes per step
+
+The first quote, backslash, or control character is found with vector
+compares, and the UTF-8 check of J. Keiser and D. Lemire covers the bytes up
+to it. Returns true with @a block at that byte; returns false with @a block at
+the start of the 16 bytes where the check found ill-formed UTF-8 or where
+fewer than 16 bytes are left, for the caller to finish one sequence at a time.
+Out of line, so that no constants of the check occupy registers in the
+caller's loop. On x86-64, it is compiled for SSSE3 (see cpu_has_ssse3()).
+*/
+JSON_SCAN_SSSE3_TARGET JSON_HEDLEY_NEVER_INLINE inline bool vector_utf8_run(const unsigned char* p, const unsigned char* e, const unsigned char*& block_out) noexcept
+{
+    using lookup = utf8_lookup4<>;
+    const unsigned char* block = p;
+#if JSON_SCAN_NEON
+    const uint8x16_t t1h = vld1q_u8(lookup::byte_1_high.data());
+    const uint8x16_t t1l = vld1q_u8(lookup::byte_1_low.data());
+    const uint8x16_t t2h = vld1q_u8(lookup::byte_2_high.data());
+    uint8x16_t prev = vdupq_n_u8(0);
+    while (e - block >= 16)
+    {
+        const uint8x16_t in = vld1q_u8(block);
+        const uint8x16_t special = vorrq_u8(vorrq_u8(vceqq_u8(in, vdupq_n_u8('"')), vceqq_u8(in, vdupq_n_u8('\\'))), vcltq_u8(in, vdupq_n_u8(0x20)));
+        const uint8x16_t prev1 = vextq_u8(prev, in, 15);
+        const uint8x16_t sc = vandq_u8(vandq_u8(vqtbl1q_u8(t1h, vshrq_n_u8(prev1, 4)), vqtbl1q_u8(t1l, vandq_u8(prev1, vdupq_n_u8(0x0F)))), vqtbl1q_u8(t2h, vshrq_n_u8(in, 4)));
+        const uint8x16_t must23 = vorrq_u8(vqsubq_u8(vextq_u8(prev, in, 14), vdupq_n_u8(0xE0 - 0x80)), vqsubq_u8(vextq_u8(prev, in, 13), vdupq_n_u8(0xF0 - 0x80)));
+        const uint8x16_t err = veorq_u8(vandq_u8(must23, vdupq_n_u8(0x80)), sc);
+        const std::uint64_t special_bits = vget_lane_u64(vreinterpret_u64_u8(vshrn_n_u16(vreinterpretq_u16_u8(special), 4)), 0);
+        const std::uint64_t err_bits = vget_lane_u64(vreinterpret_u64_u8(vshrn_n_u16(vreinterpretq_u16_u8(vtstq_u8(err, err)), 4)), 0);
+        if (special_bits != 0)
+        {
+            // errors up to the special byte count (an incomplete sequence
+            // before a quote shows at the quote); the bytes after it do not
+            const unsigned k = static_cast<unsigned>(count_trailing_zeros(special_bits)) >> 2u;
+            const std::uint64_t upto = k == 15 ? ~std::uint64_t{0} :
+                                       (std::uint64_t{1} << (4u * (k + 1u))) - 1u;
+            if ((err_bits & upto) == 0)
+            {
+                block_out = block + k;
+                return true;
+            }
+            break;
+        }
+        if (err_bits != 0)
+        {
+            break;
+        }
+        prev = in;
+        block += 16;
+    }
+#else
+    // the same with SSSE3 (pshufb for the table lookups; nibbles from 16-bit
+    // shifts, as there are no byte shifts)
+    const __m128i t1h = _mm_loadu_si128(static_cast<const __m128i*>(static_cast<const void*>(lookup::byte_1_high.data()))); // NOLINT(bugprone-casting-through-void)
+    const __m128i t1l = _mm_loadu_si128(static_cast<const __m128i*>(static_cast<const void*>(lookup::byte_1_low.data()))); // NOLINT(bugprone-casting-through-void)
+    const __m128i t2h = _mm_loadu_si128(static_cast<const __m128i*>(static_cast<const void*>(lookup::byte_2_high.data()))); // NOLINT(bugprone-casting-through-void)
+    const __m128i nibble = _mm_set1_epi8(0x0F);
+    const __m128i zero = _mm_setzero_si128();
+    __m128i prev = zero;
+    while (e - block >= 16)
+    {
+        const __m128i in = _mm_loadu_si128(static_cast<const __m128i*>(static_cast<const void*>(block))); // NOLINT(bugprone-casting-through-void)
+        const __m128i special = _mm_or_si128(_mm_or_si128(_mm_cmpeq_epi8(in, _mm_set1_epi8('"')), _mm_cmpeq_epi8(in, _mm_set1_epi8('\\'))),
+                                             _mm_cmpeq_epi8(_mm_subs_epu8(in, _mm_set1_epi8(0x1F)), zero)); // in < 0x20
+        const __m128i prev1 = _mm_alignr_epi8(in, prev, 15);
+        const __m128i sc = _mm_and_si128(_mm_and_si128(_mm_shuffle_epi8(t1h, _mm_and_si128(_mm_srli_epi16(prev1, 4), nibble)),
+                                         _mm_shuffle_epi8(t1l, _mm_and_si128(prev1, nibble))),
+                                         _mm_shuffle_epi8(t2h, _mm_and_si128(_mm_srli_epi16(in, 4), nibble)));
+        const __m128i must23 = _mm_or_si128(_mm_subs_epu8(_mm_alignr_epi8(in, prev, 14), _mm_set1_epi8(0xE0 - 0x80)),
+                                            _mm_subs_epu8(_mm_alignr_epi8(in, prev, 13), _mm_set1_epi8(0xF0 - 0x80)));
+        const __m128i err = _mm_xor_si128(_mm_and_si128(must23, _mm_set1_epi8(static_cast<char>(-128))), sc);
+        const auto special_bits = static_cast<unsigned>(_mm_movemask_epi8(special));
+        const auto err_bits = ~static_cast<unsigned>(_mm_movemask_epi8(_mm_cmpeq_epi8(err, zero))) & 0xFFFFu;
+        if (special_bits != 0)
+        {
+            const auto k = static_cast<unsigned>(count_trailing_zeros(static_cast<std::uint64_t>(special_bits)));
+            if ((err_bits & ((2u << k) - 1u)) == 0)
+            {
+                block_out = block + k;
+                return true;
+            }
+            break;
+        }
+        if (err_bits != 0)
+        {
+            break;
+        }
+        prev = in;
+        block += 16;
+    }
+#endif
+    block_out = block;
+    return false;
+}
+#endif
+
+}  // namespace detail
+NLOHMANN_JSON_NAMESPACE_END
@@ -14,6 +14,7 @@
 #include <cstring> // memcpy

 #include <nlohmann/detail/bit_ops.hpp>
+#include <nlohmann/detail/input/simd_scan.hpp>
 #include <nlohmann/detail/macro_scope.hpp>

 // Optional SIMD backend for bulk UTF-8 validation. This is an opt-in external
@@ -34,7 +35,7 @@
 // This file contains the byte-level string-scanning helpers used by the lexer's
 // contiguous fast path. They operate purely on raw bytes (no dependency on the
 // lexer's template parameters) so they are free functions, keeping the lexer
-// itself focused on the state machine; see lexer::scan_string_bulk().
+// itself focused on the state machine; see lexer::get_after_string_run().

 NLOHMANN_JSON_NAMESPACE_BEGIN
 namespace detail
@@ -66,7 +67,7 @@ inline std::uint64_t swar_string_special(std::uint64_t v) noexcept

 // return the index of the first is_string_special() byte in [data, data+n), or
 // n if every byte is ordinary; scans 8 bytes at a time
-inline std::size_t find_string_special(const unsigned char* data, std::size_t n) noexcept
+JSON_HEDLEY_ALWAYS_INLINE std::size_t find_string_special(const unsigned char* data, std::size_t n) noexcept
 {
    std::size_t i = 0;
    for (; i + 8 <= n; i += 8)
@@ -235,35 +236,143 @@ inline std::size_t valid_utf8_prefix(const unsigned char* data, std::size_t n) n
    return pos;
 }

-// Scalar (C++11) computation of the bulk run length: the number of leading
-// bytes in [data, data+n) that are ordinary ASCII or complete well-formed UTF-8
+#if JSON_SCAN_VECTOR_UTF8
+/// the end of scan_string_vector from block, where the vector loop stopped
+/// (ill-formed UTF-8, or fewer than 16 bytes left): one byte or sequence at a
+/// time, from the start of a sequence that crosses into the block
+inline const unsigned char* scan_string_finish(const unsigned char* p, const unsigned char* block, const unsigned char* e) noexcept
+{
+    for (int i = 1; i <= 3 && block - i >= p; ++i)
+    {
+        const unsigned char c = block[-i];
+        if (c < 0x80)
+        {
+            break;
+        }
+        if (c >= 0xC0)
+        {
+            const int len = 2 + static_cast<int>(c >= 0xE0) + static_cast<int>(c >= 0xF0);
+            if (len > i)
+            {
+                block -= i;
+            }
+            break;
+        }
+    }
+    for (p = block; p != e;)
+    {
+        if (*p < 0x80)
+        {
+            if (is_string_special(*p))
+            {
+                return p;
+            }
+            ++p;
+            continue;
+        }
+        const std::size_t n = validate_one_utf8(p, static_cast<std::size_t>(e - p));
+        if (n == 0)
+        {
+            return p;
+        }
+        p += n;
+    }
+    return p;
+}
+
+/// the rest of a string from p (a character boundary), with the vector UTF-8
+/// check and the scalar check for the end of the block where it stopped
+inline const unsigned char* scan_string_vector(const unsigned char* p, const unsigned char* e) noexcept
+{
+    const unsigned char* block = p;
+    if (vector_utf8_run(p, e, block))
+    {
+        return block;
+    }
+    return scan_string_finish(p, block, e);
+}
+#endif
+
+#if JSON_SCAN_VECTOR
+/// the end of the run of plain string characters at @a p: the first quote,
+/// backslash, control character, or non-ASCII byte, or @a e. The first words
+/// are checked with SWAR (one; four with NEON, where the vector mask costs
+/// more), as most keys and short values end there; longer runs continue 16
+/// bytes at a time.
+JSON_HEDLEY_ALWAYS_INLINE const unsigned char* plain_run_end(const unsigned char* p, const unsigned char* e) noexcept
+{
+    constexpr int prefix_words = JSON_SCAN_NEON ? 4 : 1;
+    for (int words = prefix_words; words > 0 && e - p >= 8; --words)
+    {
+        const std::uint64_t special = swar_string_special(read_eight_bytes(p));
+        if (special != 0)
+        {
+            return p + (static_cast<std::size_t>(count_trailing_zeros(special)) / 8);
+        }
+        p += 8;
+    }
+    // the vector loop only for 16 bytes or more: the serializer passes a
+    // string without its closing quote, so most of its runs end at e, and a
+    // call of the out-of-line NEON loop for a shorter rest made dump() up to
+    // 10% slower
+    if (e - p >= 16)
+    {
+        p = vector_plain_run_long(p, e);
+        if (e - p >= 16)
+        {
+            return p; // the vector loop stopped at a special byte
+        }
+    }
+    return p + find_string_special(p, static_cast<std::size_t>(e - p));
+}
+#endif
+
+// Computation of the bulk run length: the number of leading bytes in
+// [data, data+n) that are ordinary ASCII or complete well-formed UTF-8
 // sequences, stopping before the first byte that needs individual handling (the
 // closing quote, an escape, a control character, or an ill-formed/truncated
-// sequence). ASCII is skipped 8 bytes at a time.
-inline std::size_t scalar_string_bulk_run(const unsigned char* data, std::size_t n) noexcept
+// sequence). ASCII is skipped 16 bytes at a time with SSE2 and 8 bytes at a
+// time otherwise; runs of non-ASCII text use the vector UTF-8 check where
+// available.
+JSON_HEDLEY_ALWAYS_INLINE std::size_t scalar_string_bulk_run(const unsigned char* data, std::size_t n) noexcept
 {
-    std::size_t pos = 0;
-    while (pos < n)
+    const unsigned char* const e = data + n;
+    const unsigned char* p = data;
+    while (p != e)
    {
-        pos += find_string_special(data + pos, n - pos);
-        if (pos >= n || data[pos] < 0x80u)
+#if JSON_SCAN_VECTOR
+        p = plain_run_end(p, e);
+#else
+        p += find_string_special(p, static_cast<std::size_t>(e - p));
+#endif
+        if (p == e || *p < 0x80u)
        {
            break; // end of buffer, or a quote/escape/control byte
        }
+#if JSON_SCAN_VECTOR_UTF8
+#if JSON_SCAN_SSSE3_DISPATCH
+        if (JSON_HEDLEY_LIKELY(cpu_has_ssse3()))
+#endif
+        {
+            return static_cast<std::size_t>(scan_string_vector(p, e) - data);
+        }
+#endif
+#if !JSON_SCAN_VECTOR_UTF8 || JSON_SCAN_SSSE3_DISPATCH
        // a run of multi-byte sequences (e.g. CJK text) is validated sequence
        // by sequence without searching for the next special byte in between
        do
        {
-            const std::size_t seq = validate_one_utf8(data + pos, n - pos);
+            const std::size_t seq = validate_one_utf8(p, static_cast<std::size_t>(e - p));
            if (seq == 0)
            {
-                return pos; // ill-formed or truncated: let the byte path diagnose it
+                return static_cast<std::size_t>(p - data); // ill-formed or truncated: let the byte path diagnose it
            }
-            pos += seq;
+            p += seq;
        }
-        while (pos < n && data[pos] >= 0x80u);
+        while (p != e && *p >= 0x80u);
+#endif
    }
-    return pos;
+    return static_cast<std::size_t>(p - data);
 }

 #if defined(JSON_USE_SIMDUTF) && defined(JSON_HAS_CPP_17)
@@ -304,7 +413,7 @@ inline std::size_t find_string_delimiter(const unsigned char* data, std::size_t
 // next delimiter is validated in one shot by simdutf; on the rare failure the
 // scalar helper recomputes the exact valid prefix so the byte path still
 // produces the precise diagnostic. Without it, the pure scalar path is used.
-inline std::size_t string_bulk_run(const unsigned char* data, std::size_t n) noexcept
+JSON_HEDLEY_ALWAYS_INLINE std::size_t string_bulk_run(const unsigned char* data, std::size_t n) noexcept
 {
 #if defined(JSON_USE_SIMDUTF) && defined(JSON_HAS_CPP_17)
    const std::size_t run = find_string_delimiter(data, n);
@@ -316,6 +425,42 @@ inline std::size_t string_bulk_run(const unsigned char* data, std::size_t n) noe
    return scalar_string_bulk_run(data, n);
 }

+#if JSON_SCAN_NEON && !(defined(JSON_USE_SIMDUTF) && defined(JSON_HAS_CPP_17))
+/// scalar_string_bulk_run() from @a start on, out of line (see
+/// lexer_string_bulk_run())
+JSON_HEDLEY_NEVER_INLINE inline std::size_t string_bulk_run_from(const unsigned char* data, std::size_t start, std::size_t n) noexcept
+{
+    return start + scalar_string_bulk_run(data + start, n - start);
+}
+#endif
+
+// string_bulk_run() for the lexer. With NEON, only the first four words are
+// checked inline (most keys and short values end there), and longer runs and
+// non-ASCII text continue out of line. The lexer's scan function runs once per
+// token, and the vector code inlined into it needs more registers, which every
+// token pays for: 5% of json::accept() on jeopardy.json with Apple Clang on
+// Apple M1, even though no string of that file reaches the vector code. The
+// serializer keeps string_bulk_run() inline, which is faster there.
+JSON_HEDLEY_ALWAYS_INLINE std::size_t lexer_string_bulk_run(const unsigned char* data, std::size_t n) noexcept
+{
+#if JSON_SCAN_NEON && !(defined(JSON_USE_SIMDUTF) && defined(JSON_HAS_CPP_17))
+    std::size_t i = 0;
+    for (int words = 4; words > 0 && n - i >= 8; --words)
+    {
+        const std::uint64_t special = swar_string_special(read_eight_bytes(data + i));
+        if (special != 0)
+        {
+            const std::size_t pos = i + (static_cast<std::size_t>(count_trailing_zeros(special)) / 8);
+            return data[pos] < 0x80u ? pos : string_bulk_run_from(data, pos, n);
+        }
+        i += 8;
+    }
+    return string_bulk_run_from(data, i, n);
+#else
+    return string_bulk_run(data, n);
+#endif
+}
+
 // Decode the 4 hex digits at [data, data+4) - the digits following a `\u`
 // escape - into a codepoint 0x0000..0xFFFF via one table lookup per byte
 // (after yyjson's read_hex_u16), or return -1 if any of the 4 bytes is not a
@@ -187,6 +187,22 @@
    #endif
 #endif

+// the byte order of the target where the compiler tells it (std::endian is
+// C++20 and cannot select code in #if): JSON_LITTLE_ENDIAN_TARGET or
+// JSON_BIG_ENDIAN_TARGET is 1, or both are 0 where it is unknown (code then
+// handles the bytes one at a time); MSVC and x86 targets are little-endian
+#if defined(_MSC_VER) || defined(__x86_64__) || defined(__i386__) \
+    || (defined(__BYTE_ORDER__) && defined(__ORDER_LITTLE_ENDIAN__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__)
+    #define JSON_LITTLE_ENDIAN_TARGET 1 // NOLINT(cppcoreguidelines-macro-to-enum,modernize-macro-to-enum)
+    #define JSON_BIG_ENDIAN_TARGET 0 // NOLINT(cppcoreguidelines-macro-to-enum,modernize-macro-to-enum)
+#elif defined(__BYTE_ORDER__) && defined(__ORDER_BIG_ENDIAN__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+    #define JSON_LITTLE_ENDIAN_TARGET 0 // NOLINT(cppcoreguidelines-macro-to-enum,modernize-macro-to-enum)
+    #define JSON_BIG_ENDIAN_TARGET 1 // NOLINT(cppcoreguidelines-macro-to-enum,modernize-macro-to-enum)
+#else
+    #define JSON_LITTLE_ENDIAN_TARGET 0 // NOLINT(cppcoreguidelines-macro-to-enum,modernize-macro-to-enum)
+    #define JSON_BIG_ENDIAN_TARGET 0 // NOLINT(cppcoreguidelines-macro-to-enum,modernize-macro-to-enum)
+#endif
+
 #ifdef JSON_HAS_CPP_17
    #define JSON_INLINE_VARIABLE inline
 #else
@@ -24,6 +24,15 @@
 #undef JSON_UNLOCKED_FILE_IO
 #undef JSON_DTOA_SSE2
 #undef JSON_DTOA_NEON
+#undef JSON_LITTLE_ENDIAN_TARGET
+#undef JSON_BIG_ENDIAN_TARGET
+#undef JSON_SCAN_NEON
+#undef JSON_SCAN_SSE2
+#undef JSON_SCAN_SSSE3
+#undef JSON_SCAN_SSSE3_DISPATCH
+#undef JSON_SCAN_SSSE3_TARGET
+#undef JSON_SCAN_VECTOR
+#undef JSON_SCAN_VECTOR_UTF8

 #ifndef JSON_TEST_KEEP_MACROS
    #undef JSON_CATCH
@@ -10,17 +10,26 @@
 #pragma once

 #include <cstddef> // size_t
-#include <type_traits> // conditional, enable_if, false_type, integral_constant, is_constructible, is_integral, is_same, remove_cv, remove_reference, true_type
+#include <type_traits> // conditional, enable_if, false_type, integral_constant, is_arithmetic, is_constructible, is_integral, is_same, remove_cv, remove_reference, true_type
 #include <utility> // index_sequence, make_index_sequence, index_sequence_for

 #include <nlohmann/detail/macro_scope.hpp>

+#ifdef JSON_HAS_CPP_17
+    #include <algorithm> // clamp
+#endif
+
 NLOHMANN_JSON_NAMESPACE_BEGIN
 namespace detail
 {

-template<typename T>
-using uncvref_t = typename std::remove_cv<typename std::remove_reference<T>::type>::type;
+#ifdef __cpp_lib_remove_cvref
+    template<typename T>
+    using uncvref_t = std::remove_cvref_t<T>;
+#else
+    template<typename T>
+    using uncvref_t = typename std::remove_cv<typename std::remove_reference<T>::type>::type;
+#endif

 #ifdef JSON_HAS_CPP_14

@@ -160,5 +169,19 @@ struct static_const
    constexpr T static_const<T>::value;
 #endif

+/// @a v bounded to [@a lo, @a hi] (requires !(hi < lo)); like std::clamp,
+/// but by value, so that static constexpr members can be passed without an
+/// out-of-line definition before C++17
+template<typename T, enable_if_t<std::is_arithmetic<T>::value, int> = 0>
+constexpr T clamp(T v, T lo, T hi) noexcept
+{
+#ifdef __cpp_lib_clamp
+    return std::clamp(v, lo, hi);
+#else
+    // NOLINTNEXTLINE(readability-avoid-nested-conditional-operator): a constant expression of C++11
+    return v < lo ? lo : (hi < v ? hi : v);
+#endif
+}
+
 }  // namespace detail
 NLOHMANN_JSON_NAMESPACE_END
@@ -313,6 +313,14 @@ struct char_traits<std::byte> : std::char_traits<char>
 // is_ functions //
 ///////////////////

+#ifdef __cpp_lib_logical_traits
+
+using std::conjunction;
+using std::disjunction;
+using std::negation;
+
+#else
+
 // https://en.cppreference.com/w/cpp/types/conjunction
 template<class...> struct conjunction : std::true_type { };
 template<class B> struct conjunction<B> : B { };
@@ -330,6 +338,8 @@ struct disjunction<B, Bn...>
 // https://en.cppreference.com/w/cpp/types/negation
 template<class B> struct negation : std::integral_constant < bool, !B::value > { };

+#endif
+
 // Reimplementation of is_constructible and is_default_constructible, due to them being broken for
 // std::pair and std::tuple until LWG 2367 fix (see https://cplusplus.github.io/LWG/lwg-defects.html#2367).
 // This causes compile errors in e.g., Clang 3.5 or GCC 4.9.
@@ -1060,8 +1070,12 @@ constexpr bool value_in_range_of(T val)
    return value_in_range_of_impl1<OfType, T>::test(val);
 }

-template<bool Value>
-using bool_constant = std::integral_constant<bool, Value>;
+#ifdef __cpp_lib_bool_constant
+    using std::bool_constant;
+#else
+    template<bool Value>
+    using bool_constant = std::integral_constant<bool, Value>;
+#endif

 // Stands in for number_unsigned_t in overload sets if it is the same type as
 // number_integer_t, so that the unsigned overloads do not collide with the
@@ -55,6 +55,66 @@ using output_adapter_t = std::shared_ptr<output_adapter_protocol<CharType>>;
 /// output_vector_sink also appends writes of at least this size with insert()
 constexpr std::size_t max_reserve_size = 256;

+/// @brief copy @a length characters, at most 32, without a call of memcpy()
+///
+/// Short strings are the typical payload of a binary value, and a call of
+/// memcpy() costs more than copying them. A copy of 16 to 32 characters is two
+/// possibly overlapping 16-byte copies, one of 8 to 15 two 8-byte copies, and
+/// so on down to a single character; each is a fixed-size load and store.
+/// Nothing outside of [src, src + length) is read or written.
+template<typename CharType>
+inline void copy_short(CharType* dst, const CharType* src, const std::size_t length, std::true_type /*is_byte*/) noexcept
+{
+    JSON_ASSERT(length <= 32);
+    if (length >= 16)
+    {
+        std::array<char, 16> first; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
+        std::array<char, 16> last; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
+        std::memcpy(first.data(), src, 16);
+        std::memcpy(last.data(), src + (length - 16), 16);
+        std::memcpy(dst, first.data(), 16);
+        std::memcpy(dst + (length - 16), last.data(), 16);
+    }
+    else if (length >= 8)
+    {
+        std::array<char, 8> first; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
+        std::array<char, 8> last; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
+        std::memcpy(first.data(), src, 8);
+        std::memcpy(last.data(), src + (length - 8), 8);
+        std::memcpy(dst, first.data(), 8);
+        std::memcpy(dst + (length - 8), last.data(), 8);
+    }
+    else if (length >= 4)
+    {
+        std::array<char, 4> first; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
+        std::array<char, 4> last; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
+        std::memcpy(first.data(), src, 4);
+        std::memcpy(last.data(), src + (length - 4), 4);
+        std::memcpy(dst, first.data(), 4);
+        std::memcpy(dst + (length - 4), last.data(), 4);
+    }
+    else if (length != 0)
+    {
+        // 1 to 3: the first, the middle, and the last character
+        const CharType a = src[0];
+        const CharType b = src[length >> 1];
+        const CharType c = src[length - 1];
+        dst[0] = a;
+        dst[length >> 1] = b;
+        dst[length - 1] = c;
+    }
+}
+
+/// @brief copy @a length characters, of a character type wider than a byte
+template<typename CharType>
+inline void copy_short(CharType* dst, const CharType* src, const std::size_t length, std::false_type /*is_byte*/) noexcept
+{
+    std::memcpy(dst, src, length * sizeof(CharType));
+}
+
+/// the number of characters an empty vector is grown to by output_vector_sink
+constexpr std::size_t min_vector_sink_capacity = 64;
+
 /// @brief non-virtual output sink writing into a std::vector
 ///
 /// This sink is not part of the virtual output_adapter_protocol hierarchy: it is
@@ -78,7 +138,7 @@ class output_vector_sink
 {
  public:
    explicit output_vector_sink(std::vector<CharType, AllocatorType>& vec) noexcept
-        : v(&vec), position(vec.size())
+        : v(&vec), cursor(vec.data() + vec.size()), limit(cursor)
    {}

    output_vector_sink(const output_vector_sink&) = delete;
@@ -86,7 +146,7 @@ class output_vector_sink
    output_vector_sink& operator=(output_vector_sink&&) = delete;

    output_vector_sink(output_vector_sink&& other) noexcept
-        : v(other.v), position(other.position)
+        : v(other.v), cursor(other.cursor), limit(other.limit)
    {
        other.v = nullptr;
    }
@@ -95,7 +155,7 @@ class output_vector_sink
    {
        if (v != nullptr)
        {
-            v->resize(position);
+            v->resize(position());
        }
    }

@@ -104,11 +164,11 @@ class output_vector_sink
    JSON_HEDLEY_ALWAYS_INLINE
    void write_character(CharType c)
    {
-        if (JSON_HEDLEY_UNLIKELY(position == v->size()))
+        if (JSON_HEDLEY_UNLIKELY(cursor == limit))
        {
            grow(1);
        }
-        (*v)[position++] = c;
+        *cursor++ = c;
    }

    // no JSON_HEDLEY_NON_NULL here: binary_writer legitimately passes a null
@@ -117,7 +177,7 @@ class output_vector_sink
    JSON_HEDLEY_ALWAYS_INLINE
    void write_characters(const CharType* s, std::size_t length)
    {
-        if (JSON_HEDLEY_UNLIKELY(v->size() - position < length))
+        if (JSON_HEDLEY_UNLIKELY(space() < length))
        {
            if (length >= max_reserve_size)
            {
@@ -126,10 +186,15 @@ class output_vector_sink
            }
            grow(length);
        }
-        if (length != 0)
+        if (length <= 32)
        {
-            std::memcpy(v->data() + position, s, length * sizeof(CharType));
-            position += length;
+            copy_short(cursor, s, length, std::integral_constant<bool, sizeof(CharType) == 1>());
+            cursor += length;
+        }
+        else
+        {
+            std::memcpy(cursor, s, length * sizeof(CharType));
+            cursor += length;
        }
    }

@@ -144,21 +209,37 @@ class output_vector_sink
    CharType* reserve(const std::size_t length)
    {
        JSON_ASSERT(length <= max_reserve_size);
-        if (JSON_HEDLEY_UNLIKELY(v->size() - position < length))
+        if (JSON_HEDLEY_UNLIKELY(space() < length))
        {
            grow(length);
        }
-        return v->data() + position;
+        return cursor;
    }

    /// keep the first @a length characters written to the space from reserve()
    JSON_HEDLEY_ALWAYS_INLINE
    void commit(const std::size_t length) noexcept
    {
-        position += length;
+        cursor += length;
    }

+    /// nothing to pass on: the characters are in the vector (see output_adapter_sink)
+    void flush() noexcept
+    {}
+
  private:
+    /// number of characters of *v written so far
+    std::size_t position() const noexcept
+    {
+        return static_cast<std::size_t>(cursor - v->data());
+    }
+
+    /// number of characters that fit the vector behind the write position
+    std::size_t space() const noexcept
+    {
+        return static_cast<std::size_t>(limit - cursor);
+    }
+
    /// make room for at least @a length more characters after the position;
    /// kept out of line so that the write functions stay small enough for
    /// GCC to inline them into the writer
@@ -166,12 +247,15 @@ class output_vector_sink
    void grow(const std::size_t length)
    {
        // use the capacity the vector already has, else at least double it;
-        // never less than 64 characters, so that a small value does not
+        // never less than min_vector_sink_capacity, so that a small value does not
        // reallocate for every few bytes
-        const std::size_t needed = position + length;
-        v->resize((std::max)(std::size_t{64}, needed <= v->capacity()
+        const std::size_t written = position();
+        const std::size_t needed = written + length;
+        v->resize((std::max)(min_vector_sink_capacity, needed <= v->capacity()
                             ? v->capacity()
                             : (std::max)(needed, v->capacity() * 2)));
+        cursor = v->data() + written;
+        limit = v->data() + v->size();
    }

    /// append @a length (at least max_reserve_size) characters that do not fit
@@ -181,20 +265,24 @@ class output_vector_sink
    JSON_HEDLEY_NEVER_INLINE
    void append(const CharType* s, const std::size_t length)
    {
-        v->resize(position);
-        if (v->capacity() - position < length)
+        const std::size_t written = position();
+        v->resize(written);
+        if (v->capacity() - written < length)
        {
            // grow geometrically, with room for the writes that follow, so
            // that the next grow() need not reallocate right away
-            v->reserve((std::max)(v->capacity() * 2, position + length + max_reserve_size));
+            v->reserve((std::max)(v->capacity() * 2, written + length + max_reserve_size));
        }
        v->insert(v->end(), s, s + length);
-        position = v->size();
+        cursor = v->data() + v->size();
+        limit = cursor;
    }

    std::vector<CharType, AllocatorType>* v;
-    /// number of characters of *v written so far
-    std::size_t position;
+    /// the write position: in *v, at the number of characters written so far
+    CharType* cursor;
+    /// the end of *v
+    CharType* limit;
 };

 /// output adapter for byte vectors
@@ -277,9 +365,17 @@ class output_string_adapter : public output_adapter_protocol<CharType>
 ///
 /// Wraps the polymorphic output_adapter_t so the same binary_writer template can
 /// also target arbitrary adapters (output streams, strings, user-provided
-/// adapters) via the `output_adapter`-based overloads. Each write still goes
-/// through one virtual call, exactly as before; only the concrete sinks above
-/// avoid it.
+/// adapters) via the `output_adapter`-based overloads.
+///
+/// A write through the adapter is a virtual call, and for a stream a call with
+/// a sentry on top, which costs more than encoding the few bytes of most values.
+/// The sink therefore collects what is written in a buffer and passes it on in
+/// one piece when it is full, a write is too large for it, or @ref flush is
+/// called. Everything written reaches the adapter in the same order and with
+/// the same bytes; the destructor passes on what is left, so that a write that
+/// throws leaves the adapter with exactly the bytes written before it. Only
+/// @ref flush can report an error of the adapter (the destructor must not
+/// throw), so it has to be called once the value is written.
 template<typename CharType>
 class output_adapter_sink
 {
@@ -290,36 +386,121 @@ class output_adapter_sink
        JSON_ASSERT(oa);
    }

+    output_adapter_sink(const output_adapter_sink&) = delete;
+    output_adapter_sink& operator=(const output_adapter_sink&) = delete;
+    output_adapter_sink& operator=(output_adapter_sink&&) = delete;
+
+    output_adapter_sink(output_adapter_sink&& other) noexcept
+        : oa(std::move(other.oa)), used(other.used)
+    {
+        std::memcpy(buffer.data(), other.buffer.data(), other.used * sizeof(CharType));
+        other.used = 0;
+    }
+
+    ~output_adapter_sink()
+    {
+        // a normal return has flushed already, so this is for a write that threw
+        if (used != 0)
+        {
+            JSON_TRY
+            {
+                flush();
+            }
+            JSON_CATCH(...)
+            {
+                // nothing can be done about an adapter that throws here
+            }
+        }
+    }
+
+    JSON_HEDLEY_ALWAYS_INLINE
    void write_character(CharType c)
    {
-        oa->write_character(c);
+        if (JSON_HEDLEY_UNLIKELY(used == buffer_size))
+        {
+            flush();
+        }
+        buffer[used++] = c;
    }

    // no JSON_HEDLEY_NON_NULL: forwards (null, 0) for empty payloads, exactly as
    // the type-erased path already did before this sink existed
+    JSON_HEDLEY_ALWAYS_INLINE
    void write_characters(const CharType* s, std::size_t length)
    {
-        oa->write_characters(s, length);
+        if (JSON_HEDLEY_UNLIKELY(buffer_size - used < length))
+        {
+            write_large(s, length);
+            return;
+        }
+        if (length <= 32)
+        {
+            copy_short(buffer.data() + used, s, length, std::integral_constant<bool, sizeof(CharType) == 1>());
+            used += length;
+        }
+        else
+        {
+            std::memcpy(buffer.data() + used, s, length * sizeof(CharType));
+            used += length;
+        }
    }

    /// space for writing up to @a length characters (see
    /// output_vector_sink::reserve)
-    CharType* reserve(const std::size_t length) noexcept
+    JSON_HEDLEY_ALWAYS_INLINE
+    CharType* reserve(const std::size_t length)
    {
        JSON_ASSERT(length <= max_reserve_size);
-        static_cast<void>(length);
-        return reserved.data();
+        if (JSON_HEDLEY_UNLIKELY(buffer_size - used < length))
+        {
+            flush();
+        }
+        return buffer.data() + used;
    }

-    /// write the first @a length characters written to the space from reserve()
-    void commit(const std::size_t length)
+    /// keep the first @a length characters written to the space from reserve()
+    JSON_HEDLEY_ALWAYS_INLINE
+    void commit(const std::size_t length) noexcept
    {
-        oa->write_characters(reserved.data(), length);
+        used += length;
+    }
+
+    /// pass everything written so far on to the adapter
+    void flush()
+    {
+        if (used != 0)
+        {
+            // reset first: the characters count as written even if the adapter throws
+            const std::size_t length = used;
+            used = 0;
+            oa->write_characters(buffer.data(), length);
+        }
    }

  private:
+    /// a write that does not fit the space left in the buffer
+    JSON_HEDLEY_NEVER_INLINE
+    void write_large(const CharType* s, const std::size_t length)
+    {
+        flush();
+        if (length >= buffer_size)
+        {
+            oa->write_characters(s, length);
+        }
+        else
+        {
+            std::memcpy(buffer.data(), s, length * sizeof(CharType));
+            used = length;
+        }
+    }
+
+    /// large enough for reserve() at any time
+    static constexpr std::size_t buffer_size = 4 * max_reserve_size;
+
    output_adapter_t<CharType> oa;
-    std::array<CharType, max_reserve_size> reserved{};
+    /// number of characters of @ref buffer not yet passed on
+    std::size_t used = 0;
+    std::array<CharType, buffer_size> buffer{};
 };

 /// @brief whether std::basic_string<CharType> has a non-deprecated std::char_traits
@@ -275,11 +275,34 @@ class builder
                0, 0, '\b', 0, 0, 0, '\f', 0, 0, 0, 0, 0, 0, 0, '\n', 0, 0, 0, '\r', 0, '\t', 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
            }
        };
+        // The write position is kept in locals: the stores of characters into
+        // the arena may alias the members of the builder, which would then be
+        // reloaded after every one. It is stored back where the arena grows,
+        // and by `write_back` on every return.
+        const unsigned char* const end = m_end;
        const std::size_t start = arena_used();
-        arena_run(s, static_cast<std::size_t>(p - s));
+        char* w = m_arena_write;
+        const char* w_end = m_arena_end;
+        const arena_write_back write_back(*this, w);
+        {
+            const auto n = static_cast<std::size_t>(p - s);
+            if (n <= 16 && end - s >= 16)
+            {
+                arena_ensure(w, w_end, 16);
+                std::memcpy(w, s, 16);
+            }
+            else if (n != 0)
+            {
+                // (an empty run leaves an empty arena unallocated, and memcpy()
+                // must not be passed its null pointer even for zero bytes)
+                arena_ensure(w, w_end, n);
+                std::memcpy(w, s, n);
+            }
+            w += n;
+        }
        for (;;)
        {
-            if (p == m_end)
+            if (p == end)
            {
                return failed(error_code::string_missing_quote, p);
            }
@@ -287,7 +310,9 @@ class builder
            if (c == '"')
            {
                ++p;
-                return decoded{p, start, arena_used() - start};
+                // (from w: `write_back` stores it only after the return value
+                // is made; the arena is allocated, since an escape was written)
+                return decoded{p, start, static_cast<std::size_t>(w - m_doc.arena.data()) - start};
            }
            if (c != '\\')
            {
@@ -297,7 +322,7 @@ class builder
                return failed(c < 0x20 ? error_code::string_control_character : error_code::string_utf8, p);
            }
            ++p;
-            if (p == m_end)
+            if (p == end)
            {
                return failed(error_code::string_missing_quote, p);
            }
@@ -315,7 +340,7 @@ class builder
                    {
                        return failed(error_code::string_surrogate_low, p);
                    }
-                    if (m_end - p < 2 || p[0] != '\\' || p[1] != 'u')
+                    if (end - p < 2 || p[0] != '\\' || p[1] != 'u')
                    {
                        return failed(error_code::string_surrogate_high, p);
                    }
@@ -331,26 +356,106 @@ class builder
                    }
                    cp = 0x10000 + ((cp - 0xD800) << 10) + (lo - 0xDC00);
                }
-                arena_ensure(4);
-                m_arena_write = put_utf8(m_arena_write, cp);
+                arena_ensure(w, w_end, 4);
+                w = put_utf8(w, cp);
            }
            else if (NLOHMANN_VIEW_LIKELY(d < 128 && simple_escape[d] != 0))
            {
-                arena_ensure(1);
-                *m_arena_write++ = simple_escape[d];
+                arena_ensure(w, w_end, 1);
+                *w++ = simple_escape[d];
            }
            else
            {
                --p;
                return failed(error_code::string_escape, p);
            }
-            if (p != m_end && *p == '\\')
+#if NLOHMANN_VIEW_NEON
+            if (p != end && *p == '\\')
            {
                continue; // consecutive escapes ("\u00e4\u00f6"): no run in between
            }
+            // The first 16 bytes of the run are checked one by one, in predicted branches, and copied
+            // as one block: where the runs between escapes are short, the vector step below would put
+            // its longer dependency chain (load, compare, mask, count, add) on p for each of them,
+            // and be slower than these steps (the scanner of the keys works the same way)
+            {
+                if (end - p >= 16)
+                {
+                    const std::uint8_t* const plain = string_plain();
+                    std::size_t steps = 16;
+#define NLOHMANN_VIEW_STEP(i) if (NLOHMANN_VIEW_LIKELY(plain[p[i]] != 0)) {} else { steps = (i); goto run_found; }
+                    NLOHMANN_VIEW_REPEAT16(NLOHMANN_VIEW_STEP)
+#undef NLOHMANN_VIEW_STEP
+run_found:
+                    arena_ensure(w, w_end, 16);
+                    std::memcpy(w, p, 16); // (only the first `steps` bytes are kept)
+                    w += steps;
+                    p += steps;
+                    if (steps < 16)
+                    {
+                        if (*p >= 0x80)
+                        {
+                            // non-ASCII: the UTF-8 check, and the rest of the run
+                            const unsigned char* const r = p;
+                            p = scan_string_run(p, end);
+                            const auto n = static_cast<std::size_t>(p - r);
+                            arena_ensure(w, w_end, n);
+                            std::memcpy(w, r, n);
+                            w += n;
+                        }
+                        continue;
+                    }
+                }
+            }
+#else
+            if (p != end && (*p == '\\' || *p == '"'))
+            {
+                continue; // consecutive escapes ("\u00e4\u00f6"), or the end of the string: no run in between
+            }
+#endif
+#if NLOHMANN_VIEW_VECTOR
+            // the plain bytes up to the next quote, backslash, or control
+            // character are copied as they are scanned, 16 bytes at a time
+            for (;;)
+            {
+                if (NLOHMANN_VIEW_UNLIKELY(end - p < 16))
+                {
+                    const unsigned char* const r = p;
+                    p = scan_string_run(p, end);
+                    const auto n = static_cast<std::size_t>(p - r);
+                    arena_ensure(w, w_end, n);
+                    std::memcpy(w, r, n);
+                    w += n;
+                    break;
+                }
+                arena_ensure(w, w_end, 16);
+                const unsigned k = copy_plain_run16(p, w);
+                w += k;
+                p += k;
+                if (k == 16)
+                {
+                    continue;
+                }
+                if (NLOHMANN_VIEW_UNLIKELY(*p >= 0x80))
+                {
+                    // non-ASCII: the UTF-8 check, and the rest of the run
+                    const unsigned char* const r = p;
+                    p = scan_string_run(p, end);
+                    const auto n = static_cast<std::size_t>(p - r);
+                    arena_ensure(w, w_end, n);
+                    std::memcpy(w, r, n);
+                    w += n;
+                }
+                break;
+            }
+#else
            const unsigned char* const r = p;
-            p = scan_string_run(p, m_end);
-            arena_run(r, static_cast<std::size_t>(p - r));
+            p = scan_string_run(p, end);
+            const auto n = static_cast<std::size_t>(p - r);
+            arena_ensure(w, w_end, n);
+            std::memcpy(w, r, n);
+            w += n;
+#endif
        }
    }

@@ -392,19 +497,49 @@ class builder
    char* m_arena_write = nullptr;
    char* m_arena_end = nullptr;

+    /// room for n more bytes at w, the write position kept in a local, with
+    /// w_end the end of the arena. (A lambda instead is not always inlined,
+    /// and then w would be kept in memory, as m_arena_write is.)
+    NLOHMANN_VIEW_ALWAYS_INLINE void arena_ensure(char*& w, const char*& w_end, std::size_t n)
+    {
+        if (NLOHMANN_VIEW_UNLIKELY(static_cast<std::size_t>(w_end - w) < n))
+        {
+            m_arena_write = w;
+            arena_grow(n);
+            w = m_arena_write;
+            w_end = m_arena_end;
+        }
+    }
+
+    /// stores a write position kept in a local back into m_arena_write when
+    /// the function that keeps it returns, on every path
+    class arena_write_back
+    {
+      public:
+        arena_write_back(builder& b, char*& w) noexcept
+            : m_builder(b)
+            , m_w(w)
+        {}
+        ~arena_write_back()
+        {
+            m_builder.m_arena_write = m_w;
+        }
+
+        arena_write_back(const arena_write_back&) = delete;
+        arena_write_back& operator=(const arena_write_back&) = delete;
+        arena_write_back(arena_write_back&&) = delete;
+        arena_write_back& operator=(arena_write_back&&) = delete;
+
+      private:
+        builder& m_builder;
+        char*& m_w;
+    };
+
    NLOHMANN_VIEW_ALWAYS_INLINE std::size_t arena_used() const noexcept
    {
        return m_arena_write != nullptr ? static_cast<std::size_t>(m_arena_write - m_doc.arena.data()) : 0;
    }

-    NLOHMANN_VIEW_ALWAYS_INLINE void arena_ensure(std::size_t n)
-    {
-        if (NLOHMANN_VIEW_UNLIKELY(static_cast<std::size_t>(m_arena_end - m_arena_write) < n))
-        {
-            arena_grow(n);
-        }
-    }
-
    NLOHMANN_VIEW_NOINLINE void arena_grow(std::size_t n)
    {
        const std::size_t used = arena_used();
@@ -413,25 +548,6 @@ class builder
        m_arena_end = m_doc.arena.data() + m_doc.arena.size();
    }

-    /// append the run [r, r + n) to the arena; short runs as one fixed-size
-    /// 16-byte move when both sides have the room (no library call)
-    NLOHMANN_VIEW_ALWAYS_INLINE void arena_run(const unsigned char* r, std::size_t n)
-    {
-        if (n <= 16 && m_end - r >= 16)
-        {
-            arena_ensure(16);
-            std::memcpy(m_arena_write, r, 16);
-        }
-        else if (n != 0)
-        {
-            // (an empty run leaves an empty arena unallocated, and memcpy()
-            // must not be passed its null pointer even for zero bytes)
-            arena_ensure(n);
-            std::memcpy(m_arena_write, r, n);
-        }
-        m_arena_write += n;
-    }
-
    /// UTF-8 encoding of cp at w (room for 4 bytes); returns the position after
    /// it. (A returned pointer stays in a register; writing through a
    /// reference to m_arena_write would store and reload it around every byte.)
@@ -954,11 +1070,11 @@ indent_done:
                ++p;
            }
            const unsigned char* const int_start = p;
-            if (p != e && *p == '0')
+            if (cur() == '0')
            {
                ++p;
            }
-            else if (NLOHMANN_VIEW_LIKELY(p != e && *p >= '1' && *p <= '9'))
+            else if (NLOHMANN_VIEW_LIKELY(cur() >= '1' && cur() <= '9'))
            {
                p = skip_digits(p + 1, e);
            }
@@ -969,7 +1085,7 @@ indent_done:
            const auto int_digits = static_cast<std::size_t>(p - int_start);
            std::size_t frac_digits = 0;
            bool is_float = false;
-            if (p != e && *p == '.')
+            if (cur() == '.')
            {
                ++p;
                const unsigned char* const f0 = p;
@@ -982,20 +1098,20 @@ indent_done:
                is_float = true;
            }
            std::int64_t exponent = 0;
-            if (p != e && (*p | 0x20) == 'e')
+            if ((cur() | 0x20) == 'e')
            {
                ++p;
                bool exp_negative = false;
-                if (p != e && (*p == '+' || *p == '-'))
+                if (cur() == '+' || cur() == '-')
                {
                    exp_negative = *p == '-';
                    ++p;
                }
-                if (NLOHMANN_VIEW_UNLIKELY(p == e || !is_digit(*p)))
+                if (NLOHMANN_VIEW_UNLIKELY(!is_digit(cur())))
                {
                    return fail(error_code::number_after_exponent);
                }
-                while (p != e && is_digit(*p))
+                while (is_digit(cur()))
                {
                    if (exponent < 100000)
                    {
@@ -1057,7 +1173,7 @@ indent_done:
            ++p; // opening quote
            const unsigned char* const s = p;
            p = scan_string_run<Value>(p, e);
-            if (NLOHMANN_VIEW_LIKELY(p != e && *p == '"'))
+            if (NLOHMANN_VIEW_LIKELY(cur() == '"'))
            {
                push_node(value_t::string, 0, 0, static_cast<std::size_t>(s - b), static_cast<std::uint64_t>(p - s));
                ++p;
@@ -10,6 +10,9 @@

 #include <algorithm> // max
 #include <cstddef> // size_t
+#ifndef JSON_NO_IO
+    #include <cstdio> // FILE, fread
+#endif
 #include <istream> // istream, streambuf
 #include <string> // basic_string, char_traits, string
 #include <type_traits> // decay, integral_constant, is_array, is_const, is_integral, is_lvalue_reference, is_pointer, is_same, remove_cv, remove_extent, remove_pointer, remove_reference
@@ -154,6 +157,37 @@ inline void append_stream(std::string& buf, std::istream& is)
    is.clear(is.rdstate() | std::ios::eofbit);
 }

+/// a pointer to a C stream (never with JSON_NO_IO, which leaves out <cstdio>)
+template<typename T>
+struct is_c_stream
+#ifndef JSON_NO_IO
+    : std::is_same<T, std::FILE*>
+#else
+    : std::false_type
+#endif
+{};
+
+#ifndef JSON_NO_IO
+/// append the rest of a C stream: in blocks with fread, not character by
+/// character (the library's file adapter reads with fgetc);
+/// f is not null
+inline void append_file(std::string& buf, std::FILE* f)
+{
+    for (;;)
+    {
+        const std::size_t used = buf.size();
+        const std::size_t room = (std::max)(buf.capacity() - used, std::size_t{4096});
+        buf.resize(used + room);
+        const std::size_t got = std::fread(&buf[used], 1, room, f);
+        buf.resize(used + got);
+        if (got < room)
+        {
+            break; // end of file, or an error (as fgetc, which returns EOF for both)
+        }
+    }
+}
+#endif
+
 }  // namespace view
 }  // namespace detail
 NLOHMANN_JSON_NAMESPACE_END
@@ -147,20 +147,21 @@ class view_item

    view_item(const iterator& it, std::size_t index)
        : m_it(it)
-    {
-        if (!it.is_object_iterator())
-        {
-            m_index = std::to_string(index);
-        }
-    }
+        , m_position(index)
+    {}

-    /// the member key, or the element index for arrays
+    /// the member key, or the element index for arrays (as text made on the
+    /// first call, so that iterating over the values pays nothing for it)
    string_view_t key() const
    {
        if (m_it.is_object_iterator())
        {
            return m_it.key();
        }
+        if (m_index.empty())
+        {
+            m_index = std::to_string(m_position);
+        }
        return string_view_t(m_index.data(), m_index.size());
    }

@@ -183,7 +184,8 @@ class view_item

  private:
    iterator m_it;
-    std::string m_index{}; // NOLINT(readability-redundant-member-init)
+    std::size_t m_position; ///< the index of an array element
+    mutable std::string m_index{}; ///< the text of m_position, once key() was called // NOLINT(readability-redundant-member-init)
 };

 /// the range returned by basic_json_view::items()
@@ -166,6 +166,10 @@ const node* element_at(const document_data& d, const node* array, std::size_t id
    {
        return e + idx; // a growable block: one link per element
    }
+    if (array->next == array->len + 1u && (!nav::editable() || (array->flags & node_flags::moved) == 0))
+    {
+        return e + idx; // no element has a subtree: the elements are the nodes after the array
+    }
    for (std::size_t i = 0; i < idx; ++i)
    {
        e = document_data::after(e);
@@ -181,6 +185,10 @@ const node* last_child(const document_data& d, const node* container) noexcept
    const std::size_t value_offset = container->kind == static_cast<std::uint8_t>(value_t::object) ? 1 : 0;
    const node* const end = navigation<Editable>::end(d, container);
    const node* last = navigation<Editable>::first(d, container);
+    if (value_offset == 0 && container->next == container->len + 1u && (!navigation<Editable>::editable() || (container->flags & node_flags::moved) == 0))
+    {
+        return last + (container->len - 1u); // an array without subtrees: the elements are the nodes after it
+    }
    for (const node* c = document_data::after(last + value_offset); c != end; c = document_data::after(c + value_offset))
    {
        last = c;
@@ -8,7 +8,7 @@

 #pragma once

-#include <algorithm> // max
+#include <array> // array
 #include <cstddef> // size_t
 #include <cstdint> // int64_t, uint8_t
 #include <string> // string
@@ -40,12 +40,13 @@ template<typename BasicJsonType, bool Editable>
 BasicJsonType materialize(const document_data& d, const node* n)
 {
    using string_t = typename BasicJsonType::string_t;
-    using sax_t = json_sax_dom_parser<BasicJsonType, iterator_input_adapter<const char*>>;
+    using sax_t = json_sax_dom_parser<BasicJsonType, iterator_input_adapter<const char*>, true>;
    using nav = navigation<Editable>;

    // the open containers: their next element (or key of the next member),
-    // their end, and whether they are objects; sized once from the
-    // document's deepest nesting (for a subtree an upper bound)
+    // their end, and whether they are objects; for the first 16 levels on the
+    // stack, else sized once from the document's deepest nesting (for a
+    // subtree an upper bound)
    struct frame
    {
        const node* pos;
@@ -53,10 +54,43 @@ BasicJsonType materialize(const document_data& d, const node* n)
        bool object;
    };

+    // a scalar needs neither the handler nor the stack of open containers
+    switch (static_cast<value_t>(n->kind))
+    {
+        case value_t::string:
+            return BasicJsonType(string_t(d.str(*n), n->len));
+        case value_t::number_integer:
+            return BasicJsonType(static_cast<typename BasicJsonType::number_integer_t>(static_cast<std::int64_t>(integer_bits(*n))));
+        case value_t::number_unsigned:
+            return BasicJsonType(static_cast<typename BasicJsonType::number_unsigned_t>(integer_bits(*n)));
+        case value_t::number_float:
+            return BasicJsonType(float_value<typename BasicJsonType::number_float_t>(d, *n));
+        case value_t::boolean:
+            return BasicJsonType((n->flags & node_flags::is_true) != 0);
+        case value_t::null:
+            return BasicJsonType(nullptr);
+        case value_t::object:
+        case value_t::array:
+        case value_t::binary:
+        case value_t::discarded:
+        default:
+            break;
+    }
+
    BasicJsonType result;
    sax_t sax(result, true);
    const string_t no_token{};
-    std::vector<frame> open((std::max)(d.max_depth, std::size_t{1}));
+    // (shallow subtrees on the stack: a call for a small value then allocates only for the value)
+    std::array<frame, 16> shallow; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): filled as containers open
+    std::vector<frame> deep{};
+    frame* open = shallow.data();
+    std::size_t capacity = shallow.size();
+    if (d.max_depth > capacity)
+    {
+        deep.resize(d.max_depth);
+        open = deep.data();
+        capacity = deep.size();
+    }
    std::size_t depth = 0;
    for (;;)
    {
@@ -76,9 +110,13 @@ BasicJsonType materialize(const document_data& d, const node* n)
                {
                    sax.start_array(n->len);
                }
-                if (NLOHMANN_VIEW_UNLIKELY(depth == open.size()))
+                if (NLOHMANN_VIEW_UNLIKELY(depth == capacity))
                {
-                    open.resize(depth * 2); // (deeper than the recorded nesting, e.g. after edits)
+                    // (deeper than the recorded nesting, e.g. after edits)
+                    deep.assign(open, open + depth);
+                    deep.resize(depth * 2);
+                    open = deep.data();
+                    capacity = deep.size();
                }
                open[depth++] = frame{nav::first(d, n), nav::end(d, n), object};
                break;
@@ -105,6 +143,8 @@ BasicJsonType materialize(const document_data& d, const node* n)
            case value_t::binary:
            case value_t::discarded:
            default:
+                // false positive: the parser's frame stack points into its own storage (never null)
+                // @infer-ignore NULLPTR_DEREFERENCE
                sax.null();
                break;
        }
@@ -47,27 +47,96 @@ constexpr std::size_t index_max_displacement = 64;
 static_assert(document_data::index_min_members >= 2 * index_max_displacement,
              "a table must be much larger than the probe window of a lookup");

-/// hash of a key: its bytes, eight at a time, in a fixed byte order
+/// hash of a key: its bytes, eight at a time (in a fixed byte order), where the
+/// last word may overlap the one before (so that no loop over single bytes is
+/// needed); a key of fewer than eight bytes is read as two overlapping words of
+/// four or two bytes (in the native byte order: the hash is not stored, and the
+/// same on both sides of a lookup)
 inline std::uint64_t key_hash(const char* s, std::size_t n) noexcept
 {
    std::uint64_t h = 0x9E3779B97F4A7C15u * (n + 1);
    const auto* p = reinterpret_cast<const unsigned char*>(s); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
-    while (n >= 8)
-    {
-        h = (h ^ read_eight_bytes(p)) * 0xBF58476D1CE4E5B9u;
-        h ^= h >> 29u;
-        p += 8;
-        n -= 8;
-    }
    std::uint64_t w = 0;
-    for (std::size_t i = 0; i < n; ++i)
+    if (n >= 8)
    {
-        w |= static_cast<std::uint64_t>(p[i]) << (8u * i);
+        const unsigned char* const last = p + n - 8;
+        while (p < last)
+        {
+            h = (h ^ read_eight_bytes(p)) * 0xBF58476D1CE4E5B9u;
+            h ^= h >> 29u;
+            p += 8;
+        }
+        w = read_eight_bytes(last);
    }
-    h = (h ^ w) * 0x94D049BB133111EBu;
+    else if (n >= 4)
+    {
+        std::uint32_t head = 0;
+        std::uint32_t tail = 0;
+        std::memcpy(&head, p, 4);
+        std::memcpy(&tail, p + n - 4, 4);
+        w = static_cast<std::uint64_t>(head) | (static_cast<std::uint64_t>(tail) << 32u);
+    }
+    else if (n >= 2)
+    {
+        std::uint16_t head = 0;
+        std::uint16_t tail = 0;
+        std::memcpy(&head, p, 2);
+        std::memcpy(&tail, p + n - 2, 2);
+        w = static_cast<std::uint64_t>(head) | (static_cast<std::uint64_t>(tail) << 16u);
+    }
+    else if (n == 1)
+    {
+        w = p[0];
+    }
+    // (a product only carries bits upwards, and the slot is taken from the low
+    // bits: the high bits of the last word are folded down before the multiplication)
+    h = (h ^ w ^ (w >> 29u)) * 0x94D049BB133111EBu;
    return h ^ (h >> 31u);
 }

+/// whether the n <= 16 bytes at a and b are equal, as two overlapping words
+/// (the first and the last 8, 4, or 2 bytes) and without a call
+NLOHMANN_VIEW_ALWAYS_INLINE bool same_short_bytes(const unsigned char* a, const unsigned char* b, std::size_t n) noexcept
+{
+    if (n >= 8)
+    {
+        std::uint64_t x0 = 0;
+        std::uint64_t x1 = 0;
+        std::uint64_t y0 = 0;
+        std::uint64_t y1 = 0;
+        std::memcpy(&x0, a, 8);
+        std::memcpy(&x1, a + n - 8, 8);
+        std::memcpy(&y0, b, 8);
+        std::memcpy(&y1, b + n - 8, 8);
+        return x0 == y0 && x1 == y1;
+    }
+    if (n >= 4)
+    {
+        std::uint32_t x0 = 0;
+        std::uint32_t x1 = 0;
+        std::uint32_t y0 = 0;
+        std::uint32_t y1 = 0;
+        std::memcpy(&x0, a, 4);
+        std::memcpy(&x1, a + n - 4, 4);
+        std::memcpy(&y0, b, 4);
+        std::memcpy(&y1, b + n - 4, 4);
+        return x0 == y0 && x1 == y1;
+    }
+    if (n >= 2)
+    {
+        std::uint16_t x0 = 0;
+        std::uint16_t x1 = 0;
+        std::uint16_t y0 = 0;
+        std::uint16_t y1 = 0;
+        std::memcpy(&x0, a, 2);
+        std::memcpy(&x1, a + n - 2, 2);
+        std::memcpy(&y0, b, 2);
+        std::memcpy(&y1, b + n - 2, 2);
+        return x0 == y0 && x1 == y1;
+    }
+    return n == 0 || *a == *b;
+}
+
 /// build the table of a large object
 inline void build_object_index(document_data& d, node* obj)
 {
@@ -132,6 +201,27 @@ inline const node* find_indexed(const document_data& d, const node* obj, const c
    const document_data::object_index& ix = d.indexes[obj->extra - 1u];
    const std::uint32_t* const table = d.index_slots.data() + ix.start;
    std::size_t slot = conditional_static_cast<std::size_t>(key_hash(key, n)) & ix.mask;
+    const auto* const k_bytes = reinterpret_cast<const unsigned char*>(key); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
+    // (the loop for longer keys comes first, as the code is laid out; it is not the more common case)
+    if (NLOHMANN_VIEW_UNLIKELY(n <= 16))
+    {
+        // (up to 16 bytes, the bytes are compared as two words, without a call)
+        for (std::size_t distance = 0; distance <= index_max_displacement; ++distance)
+        {
+            const std::uint32_t s = table[slot];
+            if (s == 0)
+            {
+                return nullptr;
+            }
+            const node* const k = obj + s;
+            if (k->len == n && same_short_bytes(reinterpret_cast<const unsigned char*>(d.str(*k)), k_bytes, n)) // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
+            {
+                return k;
+            }
+            slot = (slot + 1) & ix.mask;
+        }
+        return nullptr;
+    }
    for (std::size_t distance = 0; distance <= index_max_displacement; ++distance)
    {
        const std::uint32_t s = table[slot];
@@ -23,6 +23,7 @@
 #include <nlohmann/detail/view/macro_scope.hpp>
 #include <nlohmann/detail/view/node.hpp>
 #include <nlohmann/detail/view/number.hpp>
+#include <nlohmann/detail/view/simd.hpp>

 NLOHMANN_JSON_NAMESPACE_BEGIN
 namespace detail
@@ -80,13 +81,6 @@ class output_buffer
        put(s, N - 1);
    }

-    void put_repeated(char c, std::size_t n)
-    {
-        reserve(n);
-        std::memset(m_pos, c, n);
-        m_pos += n;
-    }
-
    /// the write position and the end of the writable space, for a writer
    /// that keeps the position in a local variable (set_cursor() hands it back)
    char* cursor() const noexcept
@@ -105,17 +99,13 @@ class output_buffer
    }

  private:
-    /// the size of a growth step (a function: std::min() takes a reference,
-    /// which a static constexpr member does not have before C++17)
-    static constexpr std::size_t step() noexcept
-    {
-        return 0x10000;
-    }
+    /// the size of a growth step
+    static constexpr std::size_t step = 0x10000;

    static StringType& sized(StringType& out, std::size_t estimate)
    {
        out.reserve(estimate);
-        out.resize((std::min)((std::max)(estimate, static_cast<std::size_t>(64)), step()));
+        out.resize(detail::clamp(estimate, std::size_t{64}, step));
        return out;
    }

@@ -123,8 +113,9 @@ class output_buffer
    {
        const auto used = static_cast<std::size_t>(m_pos - m_out.data());
        // (a step does not go beyond the reserved estimate, so that a good
-        // estimate is never copied to a larger allocation)
-        const std::size_t size = (std::max)((std::min)(m_out.size() + step(), m_out.capacity()), used + n + 256);
+        // estimate is never copied to a larger allocation; not a clamp: the
+        // lower bound used + n + 256 can exceed capacity(), and then it must win)
+        const std::size_t size = (std::max)((std::min)(m_out.size() + step, m_out.capacity()), used + n + 256);
        if (size > m_out.capacity())
        {
            m_out.reserve((std::max)(m_out.capacity() * 2, size));
@@ -146,9 +137,27 @@ class output_buffer
 /// image_check::bounds can have others, which are then written unchanged).
 inline std::size_t plain_output_run(const unsigned char* s, std::size_t n) noexcept
 {
+    std::size_t i = 0;
+#if NLOHMANN_VIEW_SSE2
+    // (16 bytes per step; with NEON, the mask of a step costs more than it saves on the
+    // short runs that are typical here)
+    // NOLINTBEGIN(portability-simd-intrinsics)
+    for (; i + 16 <= n; i += 16)
+    {
+        const __m128i in = _mm_loadu_si128(static_cast<const __m128i*>(static_cast<const void*>(s + i))); // NOLINT(bugprone-casting-through-void)
+        // (a byte is below 0x20 if it is its own minimum with 0x1F)
+        const __m128i special = _mm_or_si128(_mm_or_si128(_mm_cmpeq_epi8(in, _mm_set1_epi8('"')), _mm_cmpeq_epi8(in, _mm_set1_epi8('\\'))),
+                                             _mm_cmpeq_epi8(_mm_min_epu8(in, _mm_set1_epi8(0x1F)), in));
+        const auto mask = static_cast<std::uint64_t>(static_cast<unsigned>(_mm_movemask_epi8(special)));
+        if (mask != 0)
+        {
+            return i + static_cast<std::size_t>(count_trailing_zeros(mask));
+        }
+    }
+    // NOLINTEND(portability-simd-intrinsics)
+#endif
    constexpr std::uint64_t ones = 0x0101010101010101ull;
    constexpr std::uint64_t high = 0x8080808080808080ull;
-    std::size_t i = 0;
    for (; i + 8 <= n; i += 8)
    {
        const std::uint64_t v = read_eight_bytes(s + i);
@@ -171,6 +180,98 @@ inline std::size_t plain_output_run(const unsigned char* s, std::size_t n) noexc
    return n;
 }

+/// Whether dump() with ensure_ascii writes the string at s unchanged, for a
+/// string of the source without escape sequences (which has no quote,
+/// backslash, or control character): no byte is DEL (0x7F) or above. Adding 1
+/// to each byte sets its high bit exactly for 0x7F, and a carry into the next
+/// byte only comes from 0xFF, whose own high bit is set anyway.
+inline bool is_ascii_without_delete(const char* s, std::size_t n) noexcept
+{
+    constexpr std::uint64_t ones = 0x0101010101010101ull;
+    constexpr std::uint64_t high = 0x8080808080808080ull;
+    std::size_t i = 0;
+    for (; i + 8 <= n; i += 8)
+    {
+        const std::uint64_t v = read_eight_bytes(s + i);
+        if (((v | (v + ones)) & high) != 0)
+        {
+            return false;
+        }
+    }
+    for (; i < n; ++i)
+    {
+        if (static_cast<unsigned char>(s[i]) >= 0x7F)
+        {
+            return false;
+        }
+    }
+    return true;
+}
+
+#if NLOHMANN_VIEW_VECTOR
+/// the bytes of the 16 at p that ensure_ascii cannot copy (a quote, a
+/// backslash, a control character, DEL, or not ASCII; a signed compare with
+/// 0x20 finds control characters and non-ASCII bytes at once), one bit per
+/// byte (x86) or one nibble per byte (NEON)
+NLOHMANN_VIEW_ALWAYS_INLINE std::uint64_t ascii_stop_mask(const unsigned char* p) noexcept
+{
+#if NLOHMANN_VIEW_NEON
+    const uint8x16_t in = vld1q_u8(p);
+    const uint8x16_t special = vorrq_u8(vorrq_u8(vceqq_u8(in, vdupq_n_u8('"')), vceqq_u8(in, vdupq_n_u8('\\'))),
+                                        vorrq_u8(vceqq_u8(in, vdupq_n_u8(0x7F)), vcltq_s8(vreinterpretq_s8_u8(in), vdupq_n_s8(0x20))));
+    return vget_lane_u64(vreinterpret_u64_u8(vshrn_n_u16(vreinterpretq_u16_u8(special), 4)), 0);
+#else
+    const __m128i in = _mm_loadu_si128(static_cast<const __m128i*>(static_cast<const void*>(p))); // NOLINT(bugprone-casting-through-void)
+    const __m128i special = _mm_or_si128(_mm_or_si128(_mm_cmpeq_epi8(in, _mm_set1_epi8('"')), _mm_cmpeq_epi8(in, _mm_set1_epi8('\\'))),
+                                         _mm_or_si128(_mm_cmpeq_epi8(in, _mm_set1_epi8(0x7F)), _mm_cmplt_epi8(in, _mm_set1_epi8(0x20))));
+    return static_cast<std::uint64_t>(static_cast<unsigned>(_mm_movemask_epi8(special)));
+#endif
+}
+
+/// the width in bits of a byte in the mask of ascii_stop_mask()
+constexpr unsigned ascii_stop_bits() noexcept
+{
+    return NLOHMANN_VIEW_NEON ? 4u : 1u;
+}
+#endif
+
+/// As find_ascii_copyable_run(), 16 bytes per step. end is the end of the
+/// buffer that holds the n bytes at p (a short run is read as 16 bytes if
+/// they are in the buffer).
+inline std::size_t ascii_copyable_run(const unsigned char* p, std::size_t n, const unsigned char* end) noexcept
+{
+#if NLOHMANN_VIEW_VECTOR
+    if (n >= 16)
+    {
+        std::size_t i = 0;
+        for (; i + 16 <= n; i += 16)
+        {
+            const std::uint64_t mask = ascii_stop_mask(p + i);
+            if (mask != 0)
+            {
+                return i + (static_cast<std::size_t>(count_trailing_zeros(mask)) / ascii_stop_bits());
+            }
+        }
+        if (i == n)
+        {
+            return n;
+        }
+        // the last 16 bytes: those before i are known to be copyable
+        const std::uint64_t mask = ascii_stop_mask(p + n - 16);
+        return mask != 0 ? n - 16 + (static_cast<std::size_t>(count_trailing_zeros(mask)) / ascii_stop_bits()) : n;
+    }
+    if (end - p >= 16)
+    {
+        // (the bytes after the run are masked out)
+        const std::uint64_t mask = ascii_stop_mask(p) & ((std::uint64_t{1} << (n * ascii_stop_bits())) - 1u);
+        return mask != 0 ? static_cast<std::size_t>(count_trailing_zeros(mask)) / ascii_stop_bits() : n;
+    }
+#else
+    static_cast<void>(end);
+#endif
+    return find_ascii_copyable_run(p, n);
+}
+
 /// A stack that starts in a buffer of the caller (a local array) and moves to
 /// the heap (a vector of the caller) only when that is full, so that dumps of
 /// shallow documents need no allocation. The top is a pointer, as in
@@ -250,6 +351,39 @@ NLOHMANN_VIEW_ALWAYS_INLINE char* put_literal(char* w, const char (&s)[N]) noexc
    return w + N - 1;
 }

+/// the depth of the innermost open container, counted only for indented output
+template<bool Counted>
+struct depth_counter
+{
+    std::size_t value = 0;
+    void enter() noexcept
+    {
+        ++value;
+    }
+    std::size_t leave() noexcept
+    {
+        return --value;
+    }
+    std::size_t get() const noexcept
+    {
+        return value;
+    }
+};
+
+template<>
+struct depth_counter<false>
+{
+    void enter() noexcept {}
+    std::size_t leave() noexcept // NOLINT(readability-convert-member-functions-to-static): same interface as depth_counter<true>
+    {
+        return 0;
+    }
+    std::size_t get() const noexcept // NOLINT(readability-convert-member-functions-to-static): same interface as depth_counter<true>
+    {
+        return 0;
+    }
+};
+
 /// how the view's dump() writes a value
 struct dump_style
 {
@@ -286,121 +420,258 @@ class view_serializer

    void dump(const node* root)
    {
-        if (!m_style.pretty && !m_style.ensure_ascii)
+        if (m_style.ensure_ascii)
        {
-            if (m_style.source_numbers)
-            {
-                dump_compact<true>(root);
-            }
-            else
-            {
-                dump_compact<false>(root);
-            }
-            return;
+            dump_ascii(root);
        }
-        struct frame
+        else if (m_style.pretty)
        {
-            const node* pos; ///< next element, or key of the next member
-            const node* end;
-            bool object;
-            bool first;  ///< nothing written yet
-        };
-        std::array<frame, 32> buffer; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
-        std::vector<frame> heap;
-        small_stack<frame> stack(buffer.data(), buffer.size(), heap);
-        const node* n = root;
-        for (;;)
+            dump_pretty(root);
+        }
+        else if (m_style.source_numbers)
        {
-            // write the value at n
-            if (is_container(*n))
-            {
-                const bool object = n->kind == static_cast<std::uint8_t>(value_t::object);
-                if (n->len == 0)
-                {
-                    m_out.put(object ? "{}" : "[]", 2);
-                }
-                else
-                {
-                    m_out.put(object ? '{' : '[');
-                    stack.push_back(frame{nav::first(m_doc, n), nav::end(m_doc, n), object, true});
-                }
-            }
-            else
-            {
-                write_scalar(*n);
-            }
-
-            // go to the next value: close finished containers, then separate
-            for (;;)
-            {
-                if (stack.empty())
-                {
-                    m_out.finish();
-                    return;
-                }
-                if (stack.back().pos == stack.back().end)
-                {
-                    const bool object = stack.back().object;
-                    stack.pop_back();
-                    newline(stack.size());
-                    m_out.put(object ? '}' : ']');
-                    continue;
-                }
-                frame& f = stack.back();
-                if (!f.first)
-                {
-                    m_out.put(',');
-                }
-                f.first = false;
-                newline(stack.size());
-                if (f.object)
-                {
-                    write_string(*f.pos);
-                    if (m_style.pretty)
-                    {
-                        m_out.put(": ");
-                    }
-                    else
-                    {
-                        m_out.put(':');
-                    }
-                    n = nav::value(f.pos + 1);
-                    f.pos = document_data::after(f.pos + 1);
-                }
-                else
-                {
-                    n = nav::value(f.pos);
-                    f.pos = document_data::after(f.pos);
-                }
-                break;
-            }
+            dump_text<true, false, false>(root);
+        }
+        else
+        {
+            dump_text<false, false, false>(root);
        }
    }

  private:
+    /// dump_text() with ensure_ascii, out of line: the walk without it is
+    /// faster when it is not merged with this one into dump()
+    NLOHMANN_VIEW_NOINLINE void dump_ascii(const node* root)
+    {
+        if (m_style.pretty)
+        {
+            if (m_style.source_numbers)
+            {
+                dump_text<true, true, true>(root);
+            }
+            else
+            {
+                dump_text<false, true, true>(root);
+            }
+        }
+        else if (m_style.source_numbers)
+        {
+            dump_text<true, false, true>(root);
+        }
+        else
+        {
+            dump_text<false, false, true>(root);
+        }
+    }
+
+    /// dump_text() with indentation, out of line: the compact walk is faster
+    /// when it is not merged with the indented ones into dump()
+    NLOHMANN_VIEW_NOINLINE void dump_pretty(const node* root)
+    {
+        if (m_style.source_numbers)
+        {
+            dump_text<true, true, false>(root);
+        }
+        else
+        {
+            dump_text<false, true, false>(root);
+        }
+    }
+
    /// a string that is not a plain string of the source (decoded, or written
    /// by an edit), without ensure_ascii: runs without characters to escape
-    /// are copied
-    NLOHMANN_VIEW_NOINLINE void write_decoded(const node& n)
+    /// are copied. If validate is set, the string must be valid UTF-8: the
+    /// runs are found by the lexer's scan, which validates the sequences, and
+    /// invalid UTF-8 throws what basic_json::dump() throws. (The compact output
+    /// writes the bytes of a damaged image unchanged, and scans without
+    /// validating them.)
+    NLOHMANN_VIEW_NOINLINE void write_decoded(const node& n, bool validate)
    {
        const auto* const s = reinterpret_cast<const unsigned char*>(m_doc.str(n)); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
        m_out.put('"');
        for (std::size_t i = 0; i < n.len;)
        {
-            const std::size_t run = plain_output_run(s + i, n.len - i);
+            const std::size_t run = validate ? string_bulk_run(s + i, n.len - i) : plain_output_run(s + i, n.len - i);
            if (run != 0)
            {
                m_out.put(reinterpret_cast<const char*>(s + i), run); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
                i += run;
                continue;
            }
+            if (validate && s[i] >= 0x80)
+            {
+                invalid_utf8(s, n.len); // (the scan stopped at ill-formed UTF-8)
+            }
            write_codepoint<false>(s[i], s + i, 1); // a quote, a backslash, or a control character
            ++i;
        }
        m_out.put('"');
    }

-    /// the copies of dump_compact() that are not fixed-size moves (long
+    /// whether dump_text() copies a string or key from the source: one of
+    /// the source, and with ensure_ascii one without bytes >= 0x7F (an overload
+    /// each, so that the walk without ensure_ascii is compiled exactly as
+    /// before: with GCC, a condition that only folds away later changed its
+    /// block layout and made it 4-6% slower)
+    static bool copied(const node& n, const char* /*src*/, std::false_type /*ensure_ascii*/) noexcept
+    {
+        return (n.flags & node_flags::storage) == 0;
+    }
+
+    static bool copied(const node& n, const char* src, std::true_type /*ensure_ascii*/) noexcept
+    {
+        return (n.flags & node_flags::storage) == 0 && is_ascii_without_delete(src + n.off, n.len);
+    }
+
+    /*!
+    @brief a string with ensure_ascii: the characters that are not printable ASCII as \\uXXXX
+    (a character beyond U+FFFF as a surrogate pair); strings of a document
+    are valid UTF-8, except in a damaged image loaded with image_check::bounds,
+    for which this throws what basic_json::dump() throws for the string
+    */
+    NLOHMANN_VIEW_NOINLINE void write_ascii(const node& n)
+    {
+        const auto* const s = reinterpret_cast<const unsigned char*>(m_doc.str(n)); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
+        const std::size_t size = n.len;
+        char* w = m_out.cursor();
+        char* lim = m_out.limit();
+        // room for k bytes
+        const auto room = [&](std::size_t k)
+        {
+            const auto left = static_cast<std::size_t>(lim - w);
+            if (NLOHMANN_VIEW_UNLIKELY(left < k))
+            {
+                m_out.set_cursor(w);
+                m_out.reserve(k);
+                w = m_out.cursor();
+                lim = m_out.limit();
+            }
+        };
+        static constexpr const char* hex = "0123456789abcdef";
+        // \\uXXXX
+        const auto u_escape = [&](std::uint32_t u)
+        {
+            w[0] = '\\';
+            w[1] = 'u';
+            w[2] = hex[(u >> 12u) & 0xFu];
+            w[3] = hex[(u >> 8u) & 0xFu];
+            w[4] = hex[(u >> 4u) & 0xFu];
+            w[5] = hex[u & 0xFu];
+            w += 6;
+        };
+        room(1);
+        *w++ = '"';
+        std::size_t i = 0;
+        // (a string of the source starts with a run that has nothing to escape, 16 bytes per step)
+        const std::size_t prefix = (n.flags & node_flags::storage) == 0 ? ascii_copyable_run(s, size, reinterpret_cast<const unsigned char*>(m_doc.src + m_doc.size)) : 0; // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
+        if (prefix != 0)
+        {
+            room(prefix);
+            std::memcpy(w, s, prefix);
+            w += prefix;
+            i = prefix;
+        }
+        while (i < size)
+        {
+            // (a character that needs an escape sequence is not worth a call)
+            const std::size_t run = is_ascii_copyable(s[i]) ? find_ascii_copyable_run(s + i, size - i) : 0;
+            if (run != 0)
+            {
+                room(run);
+                std::memcpy(w, s + i, run);
+                w += run;
+                i += run;
+                continue;
+            }
+            room(12);
+            if (s[i] >= 0x80)
+            {
+                const unsigned char lead = s[i];
+                // (the two-byte sequences of Latin text and the three-byte sequences of most other
+                // text, with continuation bytes of any value: the ranges that are restricted (E0,
+                // ED, and the sequences of four bytes) go through validate_one_utf8())
+                if (lead >= 0xE1 && lead <= 0xEF && lead != 0xED && size - i >= 3 && (s[i + 1] & 0xC0u) == 0x80 && (s[i + 2] & 0xC0u) == 0x80)
+                {
+                    u_escape(((lead & 0x0Fu) << 12u) | ((s[i + 1] & 0x3Fu) << 6u) | (s[i + 2] & 0x3Fu));
+                    i += 3;
+                    continue;
+                }
+                if (lead >= 0xC2 && lead <= 0xDF && size - i >= 2 && (s[i + 1] & 0xC0u) == 0x80)
+                {
+                    u_escape(((lead & 0x1Fu) << 6u) | (s[i + 1] & 0x3Fu));
+                    i += 2;
+                    continue;
+                }
+                const std::size_t len = validate_one_utf8(s + i, size - i);
+                if (NLOHMANN_VIEW_UNLIKELY(len == 0))
+                {
+                    m_out.set_cursor(w);
+                    invalid_utf8(s, size);
+                    return; // LCOV_EXCL_LINE (invalid_utf8 throws)
+                }
+                std::uint32_t codepoint = s[i] & (0xFFu >> (len + 1));
+                for (std::size_t k = 1; k < len; ++k)
+                {
+                    codepoint = (codepoint << 6u) | (s[i + k] & 0x3Fu);
+                }
+                i += len;
+                if (codepoint <= 0xFFFF)
+                {
+                    u_escape(codepoint);
+                }
+                else
+                {
+                    u_escape(0xD7C0u + (codepoint >> 10u));
+                    u_escape(0xDC00u + (codepoint & 0x3FFu));
+                }
+                continue;
+            }
+            // a quote, a backslash, or a control character (or DEL)
+            const unsigned char c = s[i++];
+            char escape = 0;
+            switch (c)
+            {
+                case 0x08:
+                    escape = 'b';
+                    break;
+                case 0x09:
+                    escape = 't';
+                    break;
+                case 0x0A:
+                    escape = 'n';
+                    break;
+                case 0x0C:
+                    escape = 'f';
+                    break;
+                case 0x0D:
+                    escape = 'r';
+                    break;
+                case 0x22:
+                    escape = '"';
+                    break;
+                case 0x5C:
+                    escape = '\\';
+                    break;
+                default:
+                    break;
+            }
+            if (escape != 0)
+            {
+                w[0] = '\\';
+                w[1] = escape;
+                w += 2;
+            }
+            else
+            {
+                u_escape(c);
+            }
+        }
+        room(1);
+        *w++ = '"';
+        m_out.set_cursor(w);
+    }
+
+    /// the copies of dump_text() that are not fixed-size moves (long
    /// strings, or near the end of the source); out of line, so that the
    /// compiler does not merge the fixed-size moves into this call
    NLOHMANN_VIEW_NOINLINE static void copy_long(char* to, const char* from, std::size_t n) noexcept
@@ -417,17 +688,19 @@ class view_serializer
    }

    /*!
-    @brief the compact output without ensure_ascii (the default dump())
+    @brief the output, compact (the default dump()) or indented, with or without ensure_ascii

    The same walk as dump(), with the write position in a local variable
    (stores through char pointers would otherwise force a reload of the
    buffer's members after each one), and with strings and number tokens of
    the source copied by fixed-size moves of 32 bytes where the source has
    that many bytes left, instead of a library call per token. The buffer
-    keeps 64 bytes of slack for the overshoot.
+    keeps 64 bytes of slack for the overshoot. With ensure_ascii (Ascii), a
+    string of the source is copied only if it has nothing to escape (see
+    copied()); any other string is written by write_ascii().
    */
-    template<bool SourceNumbers>
-    void dump_compact(const node* root)
+    template<bool SourceNumbers, bool Pretty, bool Ascii>
+    void dump_text(const node* root)
    {
        struct frame
        {
@@ -442,6 +715,16 @@ class view_serializer
        const char* const src_end = src + m_doc.size;
        char* w = m_out.cursor();
        char* lim = m_out.limit();
+        // (indented output) a line break and 63 indentation characters, from
+        // which the line break of a level of up to 63 characters is a copy
+        std::array<char, 64> ruler; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): filled below if used
+        if (Pretty)
+        {
+            ruler.fill(m_style.indent_char);
+            ruler[0] = '\n';
+        }
+        const std::size_t indent = m_style.indent;
+        depth_counter<Pretty> level; // depth of the innermost open container (indented output)
        // room for n bytes and the slack
        const auto room = [&](std::size_t n)
        {
@@ -473,12 +756,35 @@ class view_serializer
            }
            w += n;
        };
+        // (indented output) the line break and the indentation of a level
+        const auto newline = [&](std::size_t depth)
+        {
+            const std::size_t count = 1 + (depth * indent);
+            room(count);
+            if (count <= ruler.size())
+            {
+                std::memcpy(w, ruler.data(), ruler.size());
+            }
+            else
+            {
+                *w = '\n';
+                std::memset(w + 1, m_style.indent_char, count - 1);
+            }
+            w += count;
+        };
        // a string that is not a plain string of the source (out of line, so
        // that the cursor stays in a register here)
        const auto escaped = [&](const node & n)
        {
            m_out.set_cursor(w);
-            write_decoded(n);
+            if (enabled(Ascii))
+            {
+                write_ascii(n);
+            }
+            else
+            {
+                write_decoded(n, Pretty);
+            }
            w = m_out.cursor();
            lim = m_out.limit();
        };
@@ -501,7 +807,7 @@ class view_serializer
            switch (static_cast<value_t>(n->kind))
            {
                case value_t::string:
-                    if ((n->flags & node_flags::storage) == 0)
+                    if (copied(*n, src, std::integral_constant<bool, Ascii>()))
                    {
                        room(n->len + 2);
                        *w++ = '"';
@@ -578,6 +884,7 @@ class view_serializer
                    {
                        *w++ = object ? '{' : '[';
                        stack.push_back(cur);
+                        level.enter();
                        if (Editable)
                        {
                            cur = frame{nav::first(m_doc, n), nav::end(m_doc, n), object};
@@ -620,6 +927,10 @@ class view_serializer
                    {
                        break;
                    }
+                    if (Pretty)
+                    {
+                        newline(level.leave());
+                    }
                    room(1);
                    *w++ = cur.object ? '}' : ']';
                    cur = stack.back();
@@ -628,13 +939,17 @@ class view_serializer
                room(1);
                *w++ = ',';
            }
+            if (Pretty)
+            {
+                newline(level.get());
+            }
            const node* const at = Editable ? cur.pos : n;
            if (cur.object)
            {
                const node& key = *at;
-                if ((key.flags & node_flags::storage) == 0)
+                if (copied(key, src, std::integral_constant<bool, Ascii>()))
                {
-                    room(key.len + 3);
+                    room(key.len + (Pretty ? 4 : 3));
                    *w++ = '"';
                    copy(src + key.off, key.len);
                    w[0] = '"';
@@ -644,9 +959,13 @@ class view_serializer
                else
                {
                    escaped(key);
-                    room(1);
+                    room(Pretty ? 2 : 1);
                    *w++ = ':';
                }
+                if (Pretty)
+                {
+                    *w++ = ' ';
+                }
                if (Editable)
                {
                    n = nav::value(at + 1);
@@ -665,69 +984,6 @@ class view_serializer
        }
    }

-    void newline(std::size_t level)
-    {
-        if (m_style.pretty)
-        {
-            m_out.put('\n');
-            m_out.put_repeated(m_style.indent_char, level * m_style.indent);
-        }
-    }
-
-    void write_scalar(const node& n)
-    {
-        switch (static_cast<value_t>(n.kind))
-        {
-            case value_t::null:
-                m_out.put("null");
-                break;
-            case value_t::boolean:
-                if ((n.flags & node_flags::is_true) != 0)
-                {
-                    m_out.put("true");
-                }
-                else
-                {
-                    m_out.put("false");
-                }
-                break;
-            case value_t::string:
-                write_string(n);
-                break;
-            case value_t::number_integer:
-            case value_t::number_unsigned:
-            {
-                const char* const token = m_doc.str(n);
-                const std::uint32_t len = number_length(n);
-                if (!m_style.source_numbers && len == 2 && token[0] == '-' && token[1] == '0')
-                {
-                    m_out.put('0'); // parse() reads -0 as the integer 0
-                }
-                else
-                {
-                    m_out.put(token, len);
-                }
-                break;
-            }
-            case value_t::number_float:
-                if (m_style.source_numbers && (n.flags & node_flags::storage) != node_flags::edited)
-                {
-                    m_out.put(m_doc.str(n), n.len); // (a float set by an edit is written as with shortest)
-                }
-                else
-                {
-                    write_float_node(n);
-                }
-                break;
-            case value_t::object:    // LCOV_EXCL_LINE (containers are written by dump())
-            case value_t::array:     // LCOV_EXCL_LINE
-            case value_t::binary:    // LCOV_EXCL_LINE (not in a document)
-            case value_t::discarded: // LCOV_EXCL_LINE
-            default:                 // LCOV_EXCL_LINE
-                break;               // LCOV_EXCL_LINE
-        }
-    }
-
    /// a float node as dump() writes it
    void write_float_node(const node& n)
    {
@@ -794,8 +1050,7 @@ class view_serializer
    static char* write_double_value_at(char* w, double x)
    {
        // (from the bits: without the checks of to_chars())
-        std::uint64_t bits = 0;
-        std::memcpy(&bits, &x, sizeof(bits));
+        auto bits = bit_cast<std::uint64_t>(x);
        if (NLOHMANN_VIEW_UNLIKELY((bits & 0x7FF0000000000000u) == 0x7FF0000000000000u))
        {
            return write_text_at(w, "null", 4);
@@ -839,71 +1094,6 @@ class view_serializer
        m_out.put(s.data(), s.size());
    }

-    void write_string(const node& n)
-    {
-        const char* const s = m_doc.str(n);
-        m_out.put('"');
-        if ((n.flags & node_flags::storage) == 0 && !m_style.ensure_ascii)
-        {
-            // a string of the source without escape sequences has nothing to escape
-            m_out.put(s, n.len);
-        }
-        else if (m_style.ensure_ascii)
-        {
-            write_escaped<true>(reinterpret_cast<const unsigned char*>(s), n.len); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
-        }
-        else
-        {
-            write_escaped<false>(reinterpret_cast<const unsigned char*>(s), n.len); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
-        }
-        m_out.put('"');
-    }
-
-    /// as serializer::dump_escaped(); strings of a document are valid UTF-8,
-    /// except in a damaged image loaded with image_check::bounds, for which
-    /// this throws what basic_json::dump() throws for the string
-    template<bool EnsureAscii>
-    void write_escaped(const unsigned char* s, std::size_t n)
-    {
-        std::size_t i = 0;
-        while (i < n)
-        {
-            std::size_t run = 0;
-            if (!EnsureAscii)
-            {
-                run = string_bulk_run(s + i, n - i);
-            }
-            else if (is_ascii_copyable(s[i]))
-            {
-                run = find_ascii_copyable_run(s + i, n - i);
-            }
-            if (run != 0)
-            {
-                m_out.put(reinterpret_cast<const char*>(s + i), run); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
-                i += run;
-                continue;
-            }
-            std::uint32_t codepoint = s[i];
-            std::size_t len = 1;
-            if (codepoint >= 0x80)
-            {
-                len = validate_one_utf8(s + i, n - i);
-                if (NLOHMANN_VIEW_UNLIKELY(len == 0))
-                {
-                    invalid_utf8(s, n);
-                    return;
-                }
-                codepoint &= 0xFFu >> (len + 1);
-                for (std::size_t k = 1; k < len; ++k)
-                {
-                    codepoint = (codepoint << 6u) | (s[i + k] & 0x3Fu);
-                }
-            }
-            write_codepoint<EnsureAscii>(codepoint, s + i, len);
-            i += len;
-        }
-    }
-
    /// throw what basic_json::dump() throws for a string that is not valid UTF-8
    NLOHMANN_VIEW_NOINLINE static void invalid_utf8(const unsigned char* s, std::size_t n)
    {
@@ -50,7 +50,12 @@
 #endif
 #if NLOHMANN_VIEW_SSE2 && !NLOHMANN_VIEW_SSSE3 && !defined(NLOHMANN_VIEW_NO_TARGET_ATTRIBUTE) && ((defined(__clang__) && __clang_major__ >= 4) || (defined(__GNUC__) && !defined(__clang__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9))))
    // (GCC before 4.9 has no SSSE3 intrinsics without -mssse3)
-    #include <cpuid.h>
+    // <cpuid.h> of GCC before 11 has no include guard, and json.hpp and
+    // json_view.hpp both include it
+    #ifndef NLOHMANN_JSON_CPUID_INCLUDED
+        #define NLOHMANN_JSON_CPUID_INCLUDED
+        #include <cpuid.h>
+    #endif
    #include <tmmintrin.h>
    #define NLOHMANN_VIEW_SSSE3_DISPATCH 1 // NOLINT(cppcoreguidelines-macro-to-enum,modernize-macro-to-enum)
    #define NLOHMANN_VIEW_SSSE3_TARGET __attribute__((target("ssse3")))
@@ -111,6 +116,34 @@ NLOHMANN_VIEW_ALWAYS_INLINE const unsigned char* vector_plain_run(const unsigned
    }
    return p;
 }
+
+/*!
+@brief copy 16 bytes from p to w, and find the first quote, backslash,
+control character, or non-ASCII byte among them
+
+The bytes are copied whether or not they are all plain (the caller has room
+for 16 bytes and keeps only the plain ones).
+
+@return the offset of that byte, or 16 if there is none
+*/
+NLOHMANN_VIEW_ALWAYS_INLINE unsigned copy_plain_run16(const unsigned char* p, char* w) noexcept
+{
+#if NLOHMANN_VIEW_NEON
+    const uint8x16_t in = vld1q_u8(p);
+    vst1q_u8(reinterpret_cast<std::uint8_t*>(w), in); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
+    const uint8x16_t special = vorrq_u8(vorrq_u8(vceqq_u8(in, vdupq_n_u8('"')), vceqq_u8(in, vdupq_n_u8('\\'))),
+                                        vcltq_s8(vreinterpretq_s8_u8(in), vdupq_n_s8(0x20)));
+    const std::uint64_t bits = vget_lane_u64(vreinterpret_u64_u8(vshrn_n_u16(vreinterpretq_u16_u8(special), 4)), 0);
+    return bits != 0 ? static_cast<unsigned>(count_trailing_zeros(bits) >> 2u) : 16u;
+#else
+    const __m128i in = _mm_loadu_si128(static_cast<const __m128i*>(static_cast<const void*>(p))); // NOLINT(bugprone-casting-through-void)
+    _mm_storeu_si128(static_cast<__m128i*>(static_cast<void*>(w)), in); // NOLINT(bugprone-casting-through-void)
+    const __m128i special = _mm_or_si128(_mm_or_si128(_mm_cmpeq_epi8(in, _mm_set1_epi8('"')), _mm_cmpeq_epi8(in, _mm_set1_epi8('\\'))),
+                                         _mm_cmplt_epi8(in, _mm_set1_epi8(0x20)));
+    const auto bits = static_cast<std::uint64_t>(static_cast<unsigned>(_mm_movemask_epi8(special)));
+    return bits != 0 ? static_cast<unsigned>(count_trailing_zeros(bits)) : 16u;
+#endif
+}
 #endif

 #if NLOHMANN_VIEW_SSSE3_DISPATCH
@@ -19,6 +19,7 @@
 #define INCLUDE_NLOHMANN_JSON_HPP_

 #include <algorithm> // all_of, find, for_each, none_of
+#include <array> // array
 #include <cmath> // isnan
 #include <cstddef> // nullptr_t, ptrdiff_t, size_t
 #include <cstdint> // uint8_t
@@ -158,9 +159,11 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    friend class ::nlohmann::detail::binary_writer;
    template<typename BasicJsonType, typename InputType, typename SAX>
    friend class ::nlohmann::detail::binary_reader;
-    template<typename BasicJsonType, typename InputAdapterType>
+    template<typename BasicJsonType, typename InputAdapterType, bool Collect>
    friend class ::nlohmann::detail::json_sax_dom_parser;
    template<typename BasicJsonType, typename InputAdapterType>
+    friend class ::nlohmann::detail::json_sax_dom_binary_parser;
+    template<typename BasicJsonType, typename InputAdapterType>
    friend class ::nlohmann::detail::json_sax_dom_callback_parser;
 #if JSON_DIAGNOSTIC_POSITIONS
    friend struct ::nlohmann::detail::diagnostic_positions;
@@ -6287,7 +6290,7 @@ public:
           from_ubjson/from_bjdata/from_bon8/from_bson overloads

    Building the @ref binary_reader as a named local, rather than as a
-    temporary that @ref detail::json_sax_dom_parser::parse is called on in
+    temporary that @ref detail::json_sax_dom_binary_parser::parse is called on in
    the same expression, avoids a false-positive cppcheck accessMoved
    warning in each of the 16 callers.
    */
@@ -6298,7 +6301,7 @@ public:
                                       const cbor_tag_handler_t tag_handler = cbor_tag_handler_t::error)
    {
        basic_json result;
-        detail::json_sax_dom_parser<basic_json, InputAdapterType> sdp(result, allow_exceptions);
+        detail::json_sax_dom_binary_parser<basic_json, InputAdapterType> sdp(result, allow_exceptions);
        binary_reader<InputAdapterType> reader(std::move(ia), format, error_handler);
        if (!reader.sax_parse(&sdp, strict, tag_handler))
        {
@@ -6321,7 +6324,7 @@ public:
            const error_handler_t error_handler = detail::binary_writer_default_error_handler())
    {
        std::vector<std::uint8_t> result;
-        result.reserve(detail::binary_reserve_hint(j));
+        result.reserve(detail::binary_initial_capacity(j));
        vector_writer(result, error_handler).write_cbor(j);
        return result;
    }
@@ -6331,7 +6334,9 @@ public:
    static void to_cbor(const basic_json& j, detail::output_adapter<std::uint8_t> o,
                        const error_handler_t error_handler = detail::binary_writer_default_error_handler())
    {
-        binary_writer<std::uint8_t>(o, error_handler).write_cbor(j);
+        binary_writer<std::uint8_t> writer(o, error_handler);
+        writer.write_cbor(j);
+        writer.flush();
    }

    /// @brief create a CBOR serialization of a given JSON value
@@ -6339,7 +6344,9 @@ public:
    static void to_cbor(const basic_json& j, detail::output_adapter<char> o,
                        const error_handler_t error_handler = detail::binary_writer_default_error_handler())
    {
-        binary_writer<char>(o, error_handler).write_cbor(j);
+        binary_writer<char> writer(o, error_handler);
+        writer.write_cbor(j);
+        writer.flush();
    }

    /// @brief create a MessagePack serialization of a given JSON value
@@ -6348,7 +6355,7 @@ public:
            const error_handler_t error_handler = error_handler_t::keep)
    {
        std::vector<std::uint8_t> result;
-        result.reserve(detail::binary_reserve_hint(j));
+        result.reserve(detail::binary_initial_capacity(j));
        vector_writer(result, error_handler).write_msgpack(j);
        return result;
    }
@@ -6358,7 +6365,9 @@ public:
    static void to_msgpack(const basic_json& j, detail::output_adapter<std::uint8_t> o,
                           const error_handler_t error_handler = error_handler_t::keep)
    {
-        binary_writer<std::uint8_t>(o, error_handler).write_msgpack(j);
+        binary_writer<std::uint8_t> writer(o, error_handler);
+        writer.write_msgpack(j);
+        writer.flush();
    }

    /// @brief create a MessagePack serialization of a given JSON value
@@ -6366,7 +6375,9 @@ public:
    static void to_msgpack(const basic_json& j, detail::output_adapter<char> o,
                           const error_handler_t error_handler = error_handler_t::keep)
    {
-        binary_writer<char>(o, error_handler).write_msgpack(j);
+        binary_writer<char> writer(o, error_handler);
+        writer.write_msgpack(j);
+        writer.flush();
    }

    /// @brief create a UBJSON serialization of a given JSON value
@@ -6377,7 +6388,7 @@ public:
            const error_handler_t error_handler = detail::binary_writer_default_error_handler())
    {
        std::vector<std::uint8_t> result;
-        result.reserve(detail::binary_reserve_hint(j));
+        result.reserve(detail::binary_initial_capacity(j));
        vector_writer(result, error_handler).write_ubjson(j, use_size, use_type);
        return result;
    }
@@ -6388,7 +6399,9 @@ public:
                          const bool use_size = false, const bool use_type = false,
                          const error_handler_t error_handler = detail::binary_writer_default_error_handler())
    {
-        binary_writer<std::uint8_t>(o, error_handler).write_ubjson(j, use_size, use_type);
+        binary_writer<std::uint8_t> writer(o, error_handler);
+        writer.write_ubjson(j, use_size, use_type);
+        writer.flush();
    }

    /// @brief create a UBJSON serialization of a given JSON value
@@ -6397,7 +6410,9 @@ public:
                          const bool use_size = false, const bool use_type = false,
                          const error_handler_t error_handler = detail::binary_writer_default_error_handler())
    {
-        binary_writer<char>(o, error_handler).write_ubjson(j, use_size, use_type);
+        binary_writer<char> writer(o, error_handler);
+        writer.write_ubjson(j, use_size, use_type);
+        writer.flush();
    }

    /// @brief create a BJData serialization of a given JSON value
@@ -6409,7 +6424,7 @@ public:
            const error_handler_t error_handler = detail::binary_writer_default_error_handler())
    {
        std::vector<std::uint8_t> result;
-        result.reserve(detail::binary_reserve_hint(j));
+        result.reserve(detail::binary_initial_capacity(j));
        vector_writer(result, error_handler).write_ubjson(j, use_size, use_type, true, true, version);
        return result;
    }
@@ -6421,7 +6436,9 @@ public:
                          const bjdata_version_t version = bjdata_version_t::draft2,
                          const error_handler_t error_handler = detail::binary_writer_default_error_handler())
    {
-        binary_writer<std::uint8_t>(o, error_handler).write_ubjson(j, use_size, use_type, true, true, version);
+        binary_writer<std::uint8_t> writer(o, error_handler);
+        writer.write_ubjson(j, use_size, use_type, true, true, version);
+        writer.flush();
    }

    /// @brief create a BJData serialization of a given JSON value
@@ -6431,7 +6448,9 @@ public:
                          const bjdata_version_t version = bjdata_version_t::draft2,
                          const error_handler_t error_handler = detail::binary_writer_default_error_handler())
    {
-        binary_writer<char>(o, error_handler).write_ubjson(j, use_size, use_type, true, true, version);
+        binary_writer<char> writer(o, error_handler);
+        writer.write_ubjson(j, use_size, use_type, true, true, version);
+        writer.flush();
    }

    /// @brief create a BSON serialization of a given JSON value
@@ -6440,7 +6459,7 @@ public:
            const error_handler_t error_handler = detail::binary_writer_default_error_handler())
    {
        std::vector<std::uint8_t> result;
-        result.reserve(detail::binary_reserve_hint(j));
+        result.reserve(detail::binary_initial_capacity(j));
        vector_writer(result, error_handler).write_bson(j);
        return result;
    }
@@ -6450,7 +6469,9 @@ public:
    static void to_bson(const basic_json& j, detail::output_adapter<std::uint8_t> o,
                        const error_handler_t error_handler = detail::binary_writer_default_error_handler())
    {
-        binary_writer<std::uint8_t>(o, error_handler).write_bson(j);
+        binary_writer<std::uint8_t> writer(o, error_handler);
+        writer.write_bson(j);
+        writer.flush();
    }

    /// @brief create a BSON serialization of a given JSON value
@@ -6458,7 +6479,9 @@ public:
    static void to_bson(const basic_json& j, detail::output_adapter<char> o,
                        const error_handler_t error_handler = detail::binary_writer_default_error_handler())
    {
-        binary_writer<char>(o, error_handler).write_bson(j);
+        binary_writer<char> writer(o, error_handler);
+        writer.write_bson(j);
+        writer.flush();
    }

    /// @brief create a BON8 serialization of a given JSON value
@@ -6466,7 +6489,7 @@ public:
    static std::vector<std::uint8_t> to_bon8(const basic_json& j)
    {
        std::vector<std::uint8_t> result;
-        result.reserve(detail::binary_reserve_hint(j));
+        result.reserve(detail::binary_initial_capacity(j));
        vector_writer(result).write_bon8(j);
        return result;
    }
@@ -6475,14 +6498,18 @@ public:
    /// @sa https://json.nlohmann.me/api/basic_json/to_bon8/
    static void to_bon8(const basic_json& j, detail::output_adapter<std::uint8_t> o)
    {
-        binary_writer<std::uint8_t>(o).write_bon8(j);
+        binary_writer<std::uint8_t> writer(o);
+        writer.write_bon8(j);
+        writer.flush();
    }

    /// @brief create a BON8 serialization of a given JSON value
    /// @sa https://json.nlohmann.me/api/basic_json/to_bon8/
    static void to_bon8(const basic_json& j, detail::output_adapter<char> o)
    {
-        binary_writer<char>(o).write_bon8(j);
+        binary_writer<char> writer(o);
+        writer.write_bon8(j);
+        writer.flush();
    }

    /// @brief create a JSON value from an input in CBOR format
@@ -6878,6 +6905,72 @@ public:
    /// @name JSON Patch functions
    /// @{

+  private:
+    /// the members of an operation of a JSON patch that are of interest
+    struct patch_members
+    {
+        basic_json* op = nullptr;
+        basic_json* path = nullptr;
+        basic_json* value = nullptr;
+        basic_json* from = nullptr;
+    };
+
+    /// @brief find the members "op", "path", "value", and "from" of the object @a val in one pass
+    static patch_members find_patch_members(const basic_json& val, std::true_type /*key_type is string_t*/)
+    {
+        patch_members members;
+        for (auto& member : *val.m_data.m_value.object)
+        {
+            const string_t& key = member.first;
+            switch (key.size())
+            {
+                case 2:
+                    if (key == "op")
+                    {
+                        members.op = &member.second;
+                    }
+                    break;
+                case 4:
+                    if (key == "path")
+                    {
+                        members.path = &member.second;
+                    }
+                    else if (key == "from")
+                    {
+                        members.from = &member.second;
+                    }
+                    break;
+                case 5:
+                    if (key == "value")
+                    {
+                        members.value = &member.second;
+                    }
+                    break;
+                default:
+                    break;
+            }
+        }
+        return members;
+    }
+
+    /// @brief find the members by lookup for key types other than string_t
+    static patch_members find_patch_members(const basic_json& val, std::false_type /*key_type is not string_t*/)
+    {
+        const auto find_member = [&val](const char* name) -> basic_json *
+        {
+            const auto it = val.m_data.m_value.object->find(string_t(name));
+            return it != val.m_data.m_value.object->end() ? &it->second : nullptr;
+        };
+
+        patch_members members;
+        members.op = find_member("op");
+        members.path = find_member("path");
+        members.value = find_member("value");
+        members.from = find_member("from");
+        return members;
+    }
+
+  public:
    /// @brief applies a JSON patch in-place without copying the object
    /// @sa https://json.nlohmann.me/api/basic_json/patch/
    void patch_inplace(const basic_json& json_patch)
@@ -7045,31 +7138,155 @@ public:
            detail::throw_patch_not_an_array(json_patch);
        }

+        // the usual patch operations "add", "remove", "replace" and "test" on
+        // a pointer without escapes that denotes existing array elements and
+        // object members (as "add" does for the parent of the new value), as
+        // a diff creates them: apply the operation and return true; return
+        // false, with nothing changed, for all others
+        string_t token;
+        typename json_pointer::template plain_steps<basic_json> steps;
+        const auto try_plain = [&result, &token, &steps](patch_operations operation, const string_t& path, const patch_members & members, const basic_json & val)
+        {
+            if (path.empty())
+            {
+                return false;
+            }
+
+            // a missing "value" is reported below
+            const basic_json* const value_ptr = members.value;
+            const basic_json& value = value_ptr != nullptr ? *value_ptr : val;
+            if (operation != patch_operations::remove && value_ptr == nullptr)
+            {
+                return false;
+            }
+
+            switch (operation)
+            {
+                case patch_operations::replace:
+                {
+                    basic_json* const target = json_pointer::resolve_plain(&result, path, path.size(), token, steps);
+                    if (target == nullptr)
+                    {
+                        return false;
+                    }
+                    *target = value;
+                    return true;
+                }
+
+                case patch_operations::test:
+                {
+                    const basic_json* const target = json_pointer::resolve_plain(&result, path, path.size(), token, steps);
+                    // a failing test is reported below
+                    return target != nullptr && *target == value;
+                }
+
+                case patch_operations::add:
+                case patch_operations::remove:
+                {
+                    // the parent of the pointer and its last reference token
+                    std::size_t slash = path.size();
+                    while (slash > 0 && path[slash - 1] != '/')
+                    {
+                        --slash;
+                    }
+                    if (slash == 0)
+                    {
+                        return false;
+                    }
+                    --slash;
+
+                    basic_json* const parent = json_pointer::resolve_plain(&result, path, slash, token, steps);
+                    if (parent == nullptr)
+                    {
+                        return false;
+                    }
+                    token.clear();
+                    token.append(path.data() + slash + 1, path.size() - slash - 1);
+                    if (token.find_first_of('~') != string_t::npos)
+                    {
+                        return false;
+                    }
+
+                    if (operation == patch_operations::add)
+                    {
+                        if (parent->is_object())
+                        {
+                            (*parent)[token] = value;
+                            return true;
+                        }
+                        if (parent->is_array())
+                        {
+                            typename basic_json::size_type idx{};
+                            if (token == "-")
+                            {
+                                parent->push_back(value);
+                                return true;
+                            }
+                            if (json_pointer::template parse_array_index<basic_json_t>(token, idx) == json_pointer::array_index_status::ok && idx <= parent->size())
+                            {
+                                parent->insert(parent->begin() + static_cast<difference_type>(idx), value);
+                                return true;
+                            }
+                        }
+                        return false;
+                    }
+
+                    if (parent->is_object())
+                    {
+                        const auto it = parent->find(token);
+                        if (it == parent->end())
+                        {
+                            return false;
+                        }
+                        parent->erase(it);
+                        return true;
+                    }
+                    if (parent->is_array())
+                    {
+                        typename basic_json::size_type idx{};
+                        if (json_pointer::template parse_array_index<basic_json_t>(token, idx) == json_pointer::array_index_status::ok && idx < parent->size())
+                        {
+                            parent->erase(idx);
+                            return true;
+                        }
+                    }
+                    return false;
+                }
+
+                case patch_operations::move:
+                case patch_operations::copy:
+                case patch_operations::invalid:
+                default:
+                    return false;
+            }
+        };
+
+        // the name of the first member to check
+        const string_t op_member = "op";
+
        // iterate and apply the operations
        for (const auto& val : json_patch)
        {
            // wrapper to get a value for an operation
-            const auto get_value = [&val](const string_t& op,
-                                          const string_t& member,
+            const auto get_value = [&val](basic_json * found,
+                                          const string_t& op,
+                                          const char* member,
                                          bool string_type) -> basic_json &
            {
-                // find value
-                auto it = val.m_data.m_value.object->find(member);
-
                // check if the desired value is present
-                if (JSON_HEDLEY_UNLIKELY(it == val.m_data.m_value.object->end()))
+                if (JSON_HEDLEY_UNLIKELY(found == nullptr))
                {
-                    detail::throw_patch_missing_member(op, member, false, val);
+                    detail::throw_patch_missing_member(op, string_t(member), false, val);
                }

                // check if the result is of type string
-                if (JSON_HEDLEY_UNLIKELY(string_type && !it->second.is_string()))
+                if (JSON_HEDLEY_UNLIKELY(string_type && !found->is_string()))
                {
-                    detail::throw_patch_missing_member(op, member, true, val);
+                    detail::throw_patch_missing_member(op, string_t(member), true, val);
                }

                // no error: return value
-                return it->second;
+                return *found;
            };

            // type check: every element of the array must be an object
@@ -7078,16 +7295,30 @@ public:
                detail::throw_patch_not_an_array(val);
            }

+            const patch_members members = find_patch_members(val, std::is_same<typename object_t::key_type, string_t> {});
+
            // collect mandatory members
-            const string_t& op = *get_value("op", "op", true).m_data.m_value.string;
-            const string_t& path = *get_value(op, "path", true).m_data.m_value.string;
+            const string_t& op = *get_value(members.op, op_member, "op", true).m_data.m_value.string;
+            const string_t& path = *get_value(members.path, op, "path", true).m_data.m_value.string;
+            const patch_operations operation = get_op(op);
+
+            // the usual operations on a plain pointer are applied without
+            // building the pointer's reference tokens; anything else (and
+            // every error) is handled below
+            if (try_plain(operation, path, members, val))
+            {
+                continue;
+            }
+
+            // the general operations may change any container
+            steps.reset();
            json_pointer ptr(path);

-            switch (get_op(op))
+            switch (operation)
            {
                case patch_operations::add:
                {
-                    operation_add(ptr, get_value("add", "value", false));
+                    operation_add(ptr, get_value(members.value, "add", "value", false));
                    break;
                }

@@ -7100,13 +7331,13 @@ public:
                case patch_operations::replace:
                {
                    // the "path" location must exist - use at()
-                    result.at(ptr) = get_value("replace", "value", false);
+                    result.at(ptr) = get_value(members.value, "replace", "value", false);
                    break;
                }

                case patch_operations::move:
                {
-                    const string_t& from_path = *get_value("move", "from", true).m_data.m_value.string;
+                    const string_t& from_path = *get_value(members.from, "move", "from", true).m_data.m_value.string;
                    json_pointer from_ptr(from_path);

                    if (JSON_HEDLEY_UNLIKELY(is_proper_prefix(from_ptr, ptr)))
@@ -7129,7 +7360,7 @@ public:

                case patch_operations::copy:
                {
-                    const string_t& from_path = *get_value("copy", "from", true).m_data.m_value.string;
+                    const string_t& from_path = *get_value(members.from, "copy", "from", true).m_data.m_value.string;
                    const json_pointer from_ptr(from_path);

                    // The copy is functionally identical to an "add"
@@ -7147,7 +7378,7 @@ public:
                    {
                        // check if "value" matches the one at "path"
                        // the "path" location must exist - use at()
-                        success = (result.at(ptr) == get_value("test", "value", false));
+                        success = (result.at(ptr) == get_value(members.value, "test", "value", false));
                    }
                    JSON_INTERNAL_CATCH (out_of_range&)
                    {
@@ -7191,7 +7422,8 @@ public:
    {
        // the patch
        basic_json result(value_t::array);
-        diff_recursively(result, source, target, path, 0);
+        string_t buffer = path;
+        diff_recursively(result, source, target, buffer, 0);
        return result;
    }

@@ -7235,31 +7467,130 @@ public:
    // function it appears in. In diff_recursively, which is on the call stack
    // once per nesting level, that made every level cost kilobytes of stack.

+    /// @brief append an operation @a op for @a path to @a result, with @a value if it is not null
+    static void diff_operation(basic_json& result, const char* op, const string_t& path, const basic_json* value)
+    {
+        // the keys are distinct and in the order of std::map; the members are
+        // added without looking them up
+        basic_json entry(value_t::object);
+        auto& members = *entry.m_data.m_value.object;
+        auto hint = members.end();
+        json_pointer::add_flattened(members, hint, string_t("op"), string_t(op), detail::priority_tag<2> {});
+        json_pointer::add_flattened(members, hint, string_t("path"), path, detail::priority_tag<2> {});
+        if (value != nullptr)
+        {
+            json_pointer::add_flattened(members, hint, string_t("value"), *value, detail::priority_tag<2> {});
+        }
+        entry.set_parents();
+        result.push_back(std::move(entry));
+    }
+
    /// @brief append a "replace" operation for @a path with @a value to @a result
    static void diff_replace(basic_json& result, const string_t& path, const basic_json& value)
    {
-        result.push_back(
-        {
-            {"op", "replace"}, {"path", path}, {"value", value}
-        });
+        diff_operation(result, "replace", path, &value);
    }

    /// @brief append a "remove" operation for @a path to @a result
    static void diff_remove(basic_json& result, const string_t& path)
    {
-        result.push_back(object(
-        {
-            {"op", "remove"}, {"path", path}
-        }));
+        diff_operation(result, "remove", path, nullptr);
    }

    /// @brief append an "add" operation for @a path with @a value to @a result
    static void diff_add(basic_json& result, const string_t& path, const basic_json& value)
    {
-        result.push_back(
+        diff_operation(result, "add", path, &value);
+    }
+
+    /// @brief the values in the target of the members of a source object, for the
+    ///        objects of up to 16 members without allocating
+    ///
+    /// reserve() must be called with the number of values that are added.
+    class diff_target_values
+    {
+      public:
+        diff_target_values() noexcept
+            : inline_items() // NOLINT(readability-redundant-member-init)
+        {}
+        diff_target_values(const diff_target_values&) = delete;
+        diff_target_values& operator=(const diff_target_values&) = delete;
+        diff_target_values(diff_target_values&&) = delete;
+        diff_target_values& operator=(diff_target_values&&) = delete;
+        ~diff_target_values() = default;
+
+        void reserve(const std::size_t n)
        {
-            {"op", "add"}, {"path", path}, {"value", value}
-        });
+            if (n > inline_size)
+            {
+                large.resize(n);
+                items = large.data();
+            }
+        }
+
+        void push_back(const basic_json* value)
+        {
+            items[count++] = value;
+        }
+
+        std::size_t size() const noexcept
+        {
+            return count;
+        }
+
+        const basic_json* operator[](const std::size_t i) const noexcept
+        {
+            return items[i];
+        }
+
+      private:
+        static constexpr std::size_t inline_size = 16;
+        /// the values of a small object, left uninitialized: they are written
+        /// before they are read (the user-provided constructor keeps the
+        /// member initialization, which -Weffc++ asks for, from zeroing them)
+        struct uninitialized_items : std::array<const basic_json*, inline_size>
+        {
+            uninitialized_items() noexcept {} // NOLINT(modernize-use-equals-default,hicpp-use-equals-default,cppcoreguidelines-pro-type-member-init,hicpp-member-init): see above
+        };
+
+        std::size_t count = 0;
+        std::vector<const basic_json*> large{}; // NOLINT(readability-redundant-member-init)
+        uninitialized_items inline_items;
+        const basic_json** items = inline_items.data();
+    };
+
+    /// @brief append "/" and the decimal representation of @a index to @a path
+    static void diff_append_index(string_t& path, std::size_t index)
+    {
+        path.push_back('/');
+        json_pointer::append_index(path, index);
+    }
+
+    /// @brief append "/" and the escaped @a key to @a path
+    static void diff_append_key(string_t& path, const string_t& key)
+    {
+        path.push_back('/');
+        detail::escape_into(path, key);
+    }
+
+    /// @brief the path of the member @a key of the value at @a path
+    static string_t diff_key_path(const string_t& path, const string_t& key)
+    {
+        string_t result;
+        result.reserve(path.size() + key.size() + 1);
+        result.append(path.data(), path.size());
+        diff_append_key(result, key);
+        return result;
+    }
+
+    /// @brief the path of the element @a index of the value at @a path
+    static string_t diff_index_path(const string_t& path, const std::size_t index)
+    {
+        string_t result;
+        result.reserve(path.size() + 8);
+        result.append(path.data(), path.size());
+        diff_append_index(result, index);
+        return result;
    }

    /// @brief append the "remove" operations for the elements of array
@@ -7272,13 +7603,18 @@ public:
        // in that order avoids the quadratic reinsertion done before
        for (std::size_t j = source.size(); j > index; --j)
        {
-            diff_remove(result, detail::concat<string_t>(path, '/', detail::to_string<string_t>(j - 1)));
+            diff_remove(result, diff_index_path(path, j - 1));
        }

        // add other remaining elements
-        for (std::size_t i = source.size(); i < target.size(); ++i)
+        if (source.size() < target.size())
        {
-            diff_add(result, detail::concat<string_t>(path, "/-"), target[i]);
+            string_t tail_path = path;
+            tail_path.append("/-", 2);
+            for (std::size_t i = source.size(); i < target.size(); ++i)
+            {
+                diff_add(result, tail_path, target[i]);
+            }
        }
    }

@@ -7287,7 +7623,7 @@ public:
    {
        for (const auto& it : added)
        {
-            diff_add(result, detail::concat<string_t>(path, '/', detail::escape(it.key())), it.value());
+            diff_add(result, diff_key_path(path, it.key()), it.value());
        }
    }

@@ -7303,15 +7639,31 @@ public:
    operations that remove every member of @a source and add every member of
    @a target to @a result, and returns false.
    */
+    template<typename TargetValues>
    static bool diff_object_keys(basic_json& result, const basic_json& source, const basic_json& target,
-                                 const string_t& path, std::vector<const basic_json*>& target_values,
+                                 const string_t& path, TargetValues& target_values,
                                 std::vector<const_iterator>& added)
    {
        // first pass: one lookup per source key
+        // Objects of the same size usually have the same keys, in the same
+        // order: walk them together as long as that holds, which takes no lookups.
        target_values.reserve(source.size());
        std::size_t common = 0;
-        for (auto it = source.cbegin(); it != source.cend(); ++it)
+        bool together = source.size() == target.size();
+        for (auto it = source.cbegin(), partner = target.cbegin(); it != source.cend(); ++it)
        {
+            if (together)
+            {
+                if (it.key() == partner.key())
+                {
+                    target_values.push_back(&partner.value());
+                    ++common;
+                    ++partner;
+                    continue;
+                }
+                together = false;
+            }
+
            const auto found = target.find(it.key());
            if (found != target.cend())
            {
@@ -7324,6 +7676,12 @@ public:
            }
        }

+        // the same keys in the same order
+        if (together)
+        {
+            return true;
+        }
+
        // second pass: find the keys only target has. An object type that
        // keeps its members in insertion order, such as the one backing
        // ordered_json, also needs the common keys to be in the same order
@@ -7389,6 +7747,13 @@ public:
            return true;
        }

+        // equal objects, whose members are in a different order, need no
+        // operations
+        if (source == target)
+        {
+            return false;
+        }
+
        // slow path: the common keys are in a different relative
        // order in source and target (only possible for a
        // reorderable object_t like ordered_map). Building a
@@ -7405,7 +7770,7 @@ public:
        // it moves it to the end, fixing its position.
        for (auto it = source.cbegin(); it != source.cend(); ++it)
        {
-            diff_remove(result, detail::concat<string_t>(path, '/', detail::escape(it.key())));
+            diff_remove(result, diff_key_path(path, it.key()));
        }

        // add every key that is either common (just removed
@@ -7414,7 +7779,7 @@ public:
        // target exactly
        for (auto it = target.cbegin(); it != target.cend(); ++it)
        {
-            diff_add(result, detail::concat<string_t>(path, '/', detail::escape(it.key())), it.value());
+            diff_add(result, diff_key_path(path, it.key()), it.value());
        }
        return false;
    }
@@ -7423,6 +7788,9 @@ public:
    @brief @ref diff, for values at nesting level @a depth, appending the
           operations to @a result

+    @a path is the path of the values; it is a buffer that is extended and
+    shortened again below, and is the same when the function returns.
+
    Diffing two arrays or objects calls this function again, once per nesting
    level, so values nested deeply enough used to exhaust the call stack and
    terminate the process. The descent is bounded here: once @ref
@@ -7430,7 +7798,7 @@ public:
    diff_iteratively diffs what is left without the call stack.
    */
    static void diff_recursively(basic_json& result, const basic_json& source, const basic_json& target,
-                                 const string_t& path, const std::size_t depth)
+                                 string_t& path, const std::size_t depth)
    {
        // if the values are the same, there is nothing to do
        if (source == target)
@@ -7442,9 +7810,9 @@ public:
    }

    /// @brief @ref diff_recursively for values known to be unequal; callers
-    ///        compare first so they build no path for equal ones
+    ///        compare first so they extend the path only for unequal ones
    static void diff_unequal(basic_json& result, const basic_json& source, const basic_json& target,
-                             const string_t& path, const std::size_t depth)
+                             string_t& path, const std::size_t depth)
    {
        if (JSON_HEDLEY_UNLIKELY(depth >= detail::recursion_depth_limit()))
        {
@@ -7463,6 +7831,8 @@ public:
        {
            case value_t::array:
            {
+                const std::size_t path_length = path.size();
+
                // first pass: traverse common elements
                std::size_t i = 0;
                while (i < source.size() && i < target.size())
@@ -7470,7 +7840,9 @@ public:
                    // recursive call to compare array values at index i
                    if (!(source[i] == target[i]))
                    {
-                        diff_unequal(result, source[i], target[i], detail::concat<string_t>(path, '/', detail::to_string<string_t>(i)), depth + 1);
+                        diff_append_index(path, i);
+                        diff_unequal(result, source[i], target[i], path, depth + 1);
+                        path.resize(path_length);
                    }
                    ++i;
                }
@@ -7483,7 +7855,7 @@ public:

            case value_t::object:
            {
-                std::vector<const basic_json*> target_values;
+                diff_target_values target_values;
                std::vector<const_iterator> added;
                if (diff_object_keys(result, source, target, path, target_values, added))
                {
@@ -7492,6 +7864,7 @@ public:
                    // lookup is needed. Deleted keys are interleaved here
                    // too, in source's original order, to match the
                    // historical (pre-reordering-aware) output order.
+                    const std::size_t path_length = path.size();
                    std::size_t i = 0;
                    for (auto it = source.cbegin(); it != source.cend(); ++it, ++i)
                    {
@@ -7499,13 +7872,15 @@ public:
                        {
                            if (!(it.value() == *target_values[i]))
                            {
-                                diff_unequal(result, it.value(), *target_values[i], detail::concat<string_t>(path, '/', detail::escape(it.key())), depth + 1);
+                                diff_append_key(path, it.key());
+                                diff_unequal(result, it.value(), *target_values[i], path, depth + 1);
+                                path.resize(path_length);
                            }
                        }
                        else
                        {
                            // found a key that is not in target -> remove it
-                            diff_remove(result, detail::concat<string_t>(path, '/', detail::escape(it.key())));
+                            diff_remove(result, diff_key_path(path, it.key()));
                        }
                    }

@@ -7636,7 +8011,7 @@ public:
                if (i < source_array.size() && i < target_array.size())
                {
                    ++stack.back().index;
-                    detail::concat_into(current_path, '/', detail::to_string<string_t>(i));
+                    diff_append_index(current_path, i);
                    enter(source_array[i], target_array[i]);
                    if (stack.size() == depth)
                    {
@@ -7659,7 +8034,7 @@ public:
                    if (target_value_ptr != nullptr)
                    {
                        const basic_json& target_value = *target_value_ptr;
-                        detail::concat_into(current_path, '/', detail::escape(it.key()));
+                        diff_append_key(current_path, it.key());
                        enter(it.value(), target_value);
                        if (stack.size() == depth)
                        {
@@ -7669,7 +8044,7 @@ public:
                    else
                    {
                        // found a key that is not in target -> remove it
-                        diff_remove(result, detail::concat<string_t>(current_path, '/', detail::escape(it.key())));
+                        diff_remove(result, diff_key_path(current_path, it.key()));
                    }
                    continue;
                }
@@ -30,6 +30,7 @@
 #include <array> // array
 #include <cstddef> // nullptr_t, size_t // IWYU pragma: keep
 #include <cstdint> // uint8_t, uint32_t
+#include <cstdio> // FILE
 #include <cstring> // memcpy, strlen
 #include <istream> // istream // IWYU pragma: keep
 #include <iterator> // distance, input_iterator_tag, iterator_traits
@@ -295,7 +296,7 @@ class basic_json_view
            }
            detail::view::throw_type_error(305, "cannot use operator[] with a numeric argument with ", type_name());
        }
-        return idx < m_node->len ? basic_json_view(m_doc, navigation::value(detail::view::element_at<Editable>(*m_doc, m_node, idx))) : basic_json_view();
+        return idx < m_node->len ? element(idx) : basic_json_view();
    }

    /// any other integer type (int, unsigned, long, std::int64_t, ...; a
@@ -358,7 +359,7 @@ class basic_json_view
        {
            detail::view::throw_out_of_range(401, detail::concat("array index ", std::to_string(idx), " is out of range"));
        }
-        return basic_json_view(m_doc, navigation::value(detail::view::element_at<Editable>(*m_doc, m_node, idx)));
+        return element(idx);
    }

    /// any other integer type, see operator[]; negative values are out of
@@ -392,7 +393,13 @@ class basic_json_view

    string_t value(string_view_t key, const char* default_value) const
    {
-        return value(key, string_t(default_value));
+        if (NLOHMANN_VIEW_UNLIKELY(!is_object()))
+        {
+            detail::view::throw_type_error(306, "cannot use value() with ", type_name());
+        }
+        // (the default is made only if there is no such member)
+        const basic_json_view r = lookup(key);
+        return r.is_discarded() ? string_t(default_value) : r.template get<string_t>();
    }

    /// the value a JSON pointer refers to converted to T, or the default
@@ -411,7 +418,12 @@ class basic_json_view

    string_t value(const json_pointer& ptr, const char* default_value) const
    {
-        return value(ptr, string_t(default_value));
+        if (NLOHMANN_VIEW_UNLIKELY(!is_structured()))
+        {
+            detail::view::throw_type_error(306, "cannot use value() with ", type_name());
+        }
+        const basic_json_view r = detail::view::resolve_pointer(*this, detail::json_pointer_access::reference_tokens(ptr), detail::view::pointer_mode::value);
+        return r.is_discarded() ? string_t(default_value) : r.template get<string_t>();
    }

    /// the first element or member value; a primitive value itself. Throws
@@ -433,7 +445,8 @@ class basic_json_view
    {
        if (is_structured() && m_node->len != 0)
        {
-            return basic_json_view(m_doc, navigation::value(detail::view::last_child<Editable>(*m_doc, m_node) + (is_object() ? 1 : 0)));
+            return unedited() ? basic_json_view(m_doc, detail::view::last_child<false>(*m_doc, m_node) + (is_object() ? 1 : 0))
+                   : basic_json_view(m_doc, navigation::value(detail::view::last_child<Editable>(*m_doc, m_node) + (is_object() ? 1 : 0)));
        }
        return front();
    }
@@ -450,7 +463,7 @@ class basic_json_view
        {
            return end();
        }
-        const node* const k = detail::view::find_member<Editable>(*m_doc, m_node, key.data(), key.size());
+        const node* const k = find_key(key);
        return k != nullptr ? iterator(m_doc, k, true) : end();
    }

@@ -467,7 +480,7 @@ class basic_json_view
    /// whether this is an object with a member with this key
    bool contains(string_view_t key) const
    {
-        return is_object() && detail::view::find_member<Editable>(*m_doc, m_node, key.data(), key.size()) != nullptr;
+        return is_object() && find_key(key) != nullptr;
    }

    bool contains(const char* key) const
@@ -627,7 +640,14 @@ class basic_json_view
        // the compact writer keeps 64 bytes of slack, so that it does not grow
        // the buffer just before the end
        const std::size_t estimate = source_extent() + (style.pretty ? source_extent() / 2 : 0) + 160;
-        detail::view::view_serializer<BasicJsonType, Editable>(*m_doc, out, estimate, style).dump(m_node);
+        if (unedited())
+        {
+            detail::view::view_serializer<BasicJsonType, false>(*m_doc, out, estimate, style).dump(m_node);
+        }
+        else
+        {
+            detail::view::view_serializer<BasicJsonType, Editable>(*m_doc, out, estimate, style).dump(m_node);
+        }
        return out;
    }

@@ -707,7 +727,7 @@ class basic_json_view
        {
            return BasicJsonType(value_t::discarded);
        }
-        return detail::view::materialize<BasicJsonType, Editable>(*m_doc, m_node);
+        return unedited() ? detail::view::materialize<BasicJsonType, false>(*m_doc, m_node) : detail::view::materialize<BasicJsonType, Editable>(*m_doc, m_node);
    }

    /// byte offset of this value in the source text (for strings: of the
@@ -785,10 +805,50 @@ class basic_json_view
    /// (object required)
    NLOHMANN_VIEW_ALWAYS_INLINE basic_json_view lookup(string_view_t key) const noexcept
    {
+        if (unedited())
+        {
+            const node* const k = detail::view::find_member<false>(*m_doc, m_node, key.data(), key.size());
+            return k != nullptr ? basic_json_view(m_doc, k + 1) : basic_json_view();
+        }
        const node* const k = detail::view::find_member<Editable>(*m_doc, m_node, key.data(), key.size());
        return k != nullptr ? basic_json_view(m_doc, navigation::value(k + 1)) : basic_json_view();
    }

+    /// whether the document has not been edited yet: until the first edit, its index is walked like that of a
+    /// read-only document (nothing is moved or linked), which is cheaper
+    NLOHMANN_VIEW_ALWAYS_INLINE bool unedited() const noexcept
+    {
+        return !navigation::editable() || m_doc->edits == nullptr;
+    }
+
+    /// the member of this object with @a key (the last one if the key occurs more than once), or nullptr
+    NLOHMANN_VIEW_ALWAYS_INLINE const node* find_key(string_view_t key) const
+    {
+        return find_key(key, std::integral_constant<bool, Editable> {});
+    }
+
+    NLOHMANN_VIEW_ALWAYS_INLINE const node* find_key(string_view_t key, std::true_type /*editable*/) const
+    {
+        // (an editable document without edits is looked up as one that cannot be edited)
+        return unedited() ? detail::view::find_member<false>(*m_doc, m_node, key.data(), key.size())
+               : detail::view::find_member<true>(*m_doc, m_node, key.data(), key.size());
+    }
+
+    NLOHMANN_VIEW_ALWAYS_INLINE const node* find_key(string_view_t key, std::false_type /*editable*/) const
+    {
+        return detail::view::find_member<false>(*m_doc, m_node, key.data(), key.size());
+    }
+
+    /// the element of an array at an index below its size
+    NLOHMANN_VIEW_ALWAYS_INLINE basic_json_view element(size_type idx) const
+    {
+        if (unedited())
+        {
+            return basic_json_view(m_doc, detail::view::element_at<false>(*m_doc, m_node, idx));
+        }
+        return basic_json_view(m_doc, navigation::value(detail::view::element_at<Editable>(*m_doc, m_node, idx)));
+    }
+
    // --- get() dispatch ---

    bool get_impl(detail::view::value_tag<bool> /*unused*/, detail::priority_tag<2> /*unused*/) const
@@ -1528,7 +1588,8 @@ class basic_json_document
        // NOLINTBEGIN(readability-avoid-nested-conditional-operator): a constant expression of C++11
        append_input_impl(buf, std::forward<T>(input), std::integral_constant < int, detail::is_contiguous_byte_container<D>::value ? 0
                          : std::is_base_of<std::istream, D>::value ? 1
-                          : detail::view::is_adapter_input<D>::value ? 2 : 3 > {});
+                          : detail::view::is_adapter_input<D>::value ? 2
+                          : detail::view::is_c_stream<D>::value ? 4 : 3 > {});
        // NOLINTEND(readability-avoid-nested-conditional-operator)
    }

@@ -1550,6 +1611,19 @@ class basic_json_document
        detail::view::append_adapter(buf, std::move(input.ia));
    }

+#ifndef JSON_NO_IO
+    static void append_input_impl(std::string& buf, std::FILE* file, std::integral_constant<int, 4> /*C stream*/)
+    {
+        if (file == nullptr)
+        {
+            // (as before: the library's adapter decides what a null stream yields)
+            detail::view::append_adapter(buf, detail::input_adapter(file));
+            return;
+        }
+        detail::view::append_file(buf, file);
+    }
+#endif
+
    template<typename T>
    static void append_input_impl(std::string& buf, T&& input, std::integral_constant<int, 3> /*other*/)
    {